The meetup scheduled for October 18, 2024 in the Marriott room at the Campus Center following the UMass Chan Medical School retreat is shaping up to be a lively event with trivia, 1 – minute data blitz, numerous networking opportunities, catering and refreshments, and an opportunity to share your research by presenting a poster. Registration is still open for poster presenting and we ask that you register in advance so that we can provide enough poster stands for all.
Below you’ll find some of the abstracts and/or titles of just some of the presenters already registered.
1. Greg Pearson, UMass Amherst, Neuroscience
TITLE. Time of day primes the olfactory bulb to differentially respond to an intranasal virus-like challenge PURPOSE. Neuroimmune responses are critical for survival. This is particularly evident with neurotropic (brain-targeting) pathogens, in which impaired immune signaling following infection results in severe neuropathology and death. We previously found that the severity of neurotropic virus infection is impacted by time of day of infection. However, the mechanism by which time of day modulates this survival outcome remains unknown. We have previously demonstrated that the olfactory bulb (OB), a site of neurotropic virus entry into the brain, rhythmically expresses neuroinflammation-related transcripts. These rhythmically expressed transcripts are enriched in genes associated with functional aspects of microglia. We also found that antiviral-related transcripts are upregulated in the OB at active phase onset, a time of day associated with enhanced survival following neurotropic virus infection. Here, we tested the hypothesis that time of day primes the OB to differentially respond to an intranasal virus-like challenge. METHODS. For Experiment 1, we intranasally challenged male mice (age = 15 weeks) at resting phase onset (ZT0) or active phase onset (ZT12) with vehicle or poly(I:C) and collected tissues at 0-, 3-, 12-, and 24-hours post-inoculation (n = 4 mice/inoculation ZT/collection time, total n = 32 mice). OB transcriptional responses were measured using NanoString technology. For Experiment 2, we intranasally challenged male mice (age = 13 weeks) with vehicle or poly(I:C) at ZT0 or ZT12 (n = 4 mice/inoculation ZT/treatment, total n = 16 mice). We then isolated OB microglia at 24 hours post-inoculation and used imaging flow cytometry to analyze a population of cells characteristic of microglia. RESULTS. For Experiment 1, we found that intranasal poly(I:C) induced antiviral responses in the OB and that these responses unfolded more rapidly in mice challenged at ZT12 compared to ZT0. For Experiment 2, we found that time of day altered the number of OB microglia independent of treatment, with more OB microglia at ZT12 than ZT0. Surprisingly, we also observed a high proportion of microglia that contained intrinsically fluorescent puncta. The number of intrinsically fluorescent microglia were reduced following intranasal poly(I:C) at both ZT0 and ZT12, but this reduction was enhanced at ZT12. CONCLUSIONS. Time of day primes the OB to mount differential antiviral and microglial responses to intranasal virus-like stimuli, which may provide an antiviral gating mechanism underlying differential susceptibility to neurotropic virus exposure via the nasal route.
2. Kathryn Nippert, UMass Amherst, Neuroscience
Alcohol use disorder (AUD) is characterized by compulsive alcohol-seeking despite associated negative outcomes. This behavioral phenotype, commonly present in humans with AUD, may in part be a result of impaired flexible behavior. Inflexibility has been identified as both a result of and risk factor for AUD. The present research aimed to track changes in flexible behavior across alcohol and stress exposure using a novel operant attentional set shifting task (ASST).
3. Michael Bahiru, UMass Amherst, Neuroscience
Effects of Cryptochrome 1 deletion on suprachiasmatic function under jet lag conditions
4. Danielle Adank, UMass Chan Medical School, Neurobiology
Prior exposure to voluntary wheel running promotes aversion-resistant ethanol intake in mice.
Danielle N. Adank, Nicholas Petersen, Yizhen Quan, Danny G. Winder
Vanderbilt University, Center for Research Addiction, Nashville, TN, 37232, United States
Vanderbilt University, Vanderbilt Brain Institute, Nashville, TN, 37232, United States
University of Massachusetts Chan Medical School, Department of Neurobiology, Worcester, MA, 01655, United States
Alcohol use disorder (AUD) is a chronic relapsing condition often driven by negative affective states. We and others have demonstrated in mice that voluntary wheel running during forced abstinence can ameliorate negative affective states. To date, clinical research examining how exercise and physical activity influence alcohol-drinking behaviors is mixed. Since exercise and physical activity are critical parts of living, understanding how physical activity influences alcohol drinking is essential for approaching individual-based care for AUD. Further, it is unknown if active individuals exhibit different alcohol-drinking behaviors compared to those that are inactive. We developed a novel wheel technology called LIQ-WID (Lick Instance Quantifier-Wheel Integrated Device), which we used to collect time-linked lick and wheel-running behavior. Here, we explored the impact of wheel running on alcohol intake when wheel running is initiated before alcohol availability. Prior wheel availability did not alter home cage continuous access ethanol intake. However, exercise was associated with reduced quinine sensitivity in ethanol drinking. When given increasing increments of quinine, mice with pre-exposure to wheel-running displayed increased aversion resistance behaviors via increased alcohol preference. Our LIQ lick structure analysis revealed that these running wheel mice exposed to quinine had a greater amount of licks, as well as increased lick and bout durations, compared to mice exposed to a locked wheel. We conclude that prior exposure to wheel running does not change alcohol drinking but may promote maladaptive drinking behaviors in mice. Although further studies are needed, such data provide further insight into potential reasons for the complex landscape of clinical data on exercise and AUD.
5. Margot Schmitt, UMass Amherst, Neuroscience
Aging is associated with cognitive decline and a reduction of frontotemporal corticocortical white matter tracts. In 2022, 18.4% of those aged 60-64 and 9.7% of those 65+ reported binge drinking alcohol within the previous month. Heavy alcohol use in older populations may accelerate the loss of white matter and worsen cognitive functioning, impacting other diseases of aging including frontotemporal dementias. Oligodendrocytes (OLs) are the myelinating cells of the central nervous system, wrapping axons in the protein-lipid rich myelin sheath, speeding up signal transduction. To begin exploring the relationship between binge drinking, cognition, and OLs in older adults we tested cognitive and drinking behaviors in a double transgenic mouse reporter line that conditionally tags OL precursor cells (OPCs) with enhanced yellow fluorescent protein (eYFP) following tamoxifen administration. Seventeen-month-old Pdgfr alpha-CreERTM-eYFP mice (N=12) were tested for baseline cognitive functioning using the object location and novel object recognition tasks (OL/NOR). They were then injected with tamoxifen to induce Cre-recombination, followed by 10 weeks of voluntary ethanol (unsweetened 20%v/v) (n=6) or water (n=6) using a drinking in the dark (DID) model. Post-drinking OL/NOR testing was done one week following the last bout of drinking. We found that voluntary alcohol intake increased over the 10-week DID period, with individual average alcohol consumption ranging from 2.02ml/kg to 11.65ml/kg per session with a group average of 6.73 ± 3.31 ml/kg. The water group consumed from 7.74 ml/kg to 27.38 ml/kg per session with a group average of 18.53 ± 6.17 ml/kg. Baseline 24-hour NOR performance showed a robust correlation with average alcohol intake, with worse performing mice showing greater voluntary alcohol intake. Conversely, baseline levels of short-term location or recognition memory did not predict subsequent alcohol intake and those drinking levels did not relate to future cognitive performance on the OL/NOR tasks (post-alcohol). Immunohistochemical experiments using a combination of cellular markers are being used to determine if lower cognitive abilities and higher drinking are associated with delays in oligodendroglial differentiation and maturation. These experiments will help shape future studies identifying predictors and consequences of late in life alcohol use.
6. Annabelle Flores Bonilla, UMass Amherst, Neuroscience
In the United States, approximately 11.1 million 12–25-year-olds reported binge drinking in 2022. Adolescent brains undergo substantial changes in neurocircuitry as oligodendrocytes (OLs) rapidly myelinate active axons which facilitates faster propagation of action potentials. The central amygdala (CeA) is enriched with cells expressing the stress response modulator corticotropin-releasing factor (CRF) peptide. Alcohol increases CeA cell activity and inhibiting CRF signaling in the CeA decreases alcohol consumption. Escalation in alcohol drinking has also been linked to genes involved in OL differentiation and myelin. A goal of this study is to understand how CRF and OLs may interact to affect alcohol drinking. We hypothesize that adolescent alcohol impacts the myelination of axons coming into and leaving the CeA. We used NG2-CreERTM; Tau-mGFP male and female transgenic mice to tag differentiating OLs with membrane-bound green fluorescent protein (GFP) and track the formation of new (de novo) myelin sheaths during adolescence. Following tamoxifen-induced Cre-recombination on postnatal days (P) 21-24, mice had access to water (n=5/sex) or alcohol (unsweetened 20%v/v) (n=4-5/sex) using a drinking-in-the-dark voluntary binge drinking model throughout early adolescence (P28-42). Drinking significantly escalated in the two weeks of access (t-test, p<0.05), with an average alcohol consumption of 3.3 0.4 g/kg/4h in the first week and 4.6 0.3 g/kg/4h in the second week. Mice were perfused and brains were collected after two months of abstinence. Brains were processed for immunohistochemical co-labeling of GFP and CRF proteins and counterstained with the fluorescent nuclear marker Hoechst. Confocal images were acquired using the CREST-V2 at 60X oil magnification with z-stacks of the CeA. CRF peptide expression was found higher in the CeA of females compared to males (main effect of sex, p<0.05). We also found evidence for de novo myelin sheaths (GFP+ fibers) in the CeA during adolescence and early adulthood in all groups. De novo myelination was higher in the alcohol group compared to water group only in males (treatment x sex interaction and Bonferroni post-hoc analysis, ps<0.05). These findings suggest alcohol impacts stress circuitry by increasing de novo myelination of axons interacting with CRF cells in the CeA.
7. Stephanie Puig, UMass Chan Medical School, Neurobiology
Despite the prevalence of opioid misuse, opioids remain the gold-standard for severe pain. Unfortunately, chronic opioid use requires dose-escalation due to the development of tolerance, which augments the propensity of opioid use disorders (OUD, addiction). Opioids signal via µ-opioid receptors (MOR) expressed in pain processing neurons. A challenge in opioid research is to identify signaling pathways downstream of the MOR that could be targeted to prevent or treat side-effects without altering analgesia. We recently discovered that opioid administration in rodents leads to activation of the platelet-derived growth factor receptor beta (PDGFRβ) downstream of MOR. Accordingly, we found that co-administration of opioids with imatinib, a PDGFRβ inhibitor, prevents the expression of analgesic tolerance. However, the mechanisms are largely unknown. In addition, in recent pilot studies, we discovered that PDGFRβ is expressed in brain structures that mediate reward, suggesting that it could also be involved in the mechanisms leading to OUD. Together, we hypothesize that undesirable side effects of clinically used opioids could be eliminated by targeting PDGFRβ signaling. Our laboratory uses rodent behavioral pharmacology, optogenetics, biochemistry, multiplex immunohistochemistry and in situ hybridization, microscopy to investigate the mechanisms underlying PDGFRβ-mediated tolerance and opioid reward.
We discovered that targeting PDGFRβ signaling blocks peripheral opioid tolerance: rodent optogenetic and tissue imaging studies showed that PDGFRβ could be activated on primary sensory neurons via mechanisms involving opioid-mediated release of platelet-derived- growth factor type B (PDGF-B) ligand from skin keratinocytes. In parallel, we discovered that imatinib administration blocks the expression of opioid reward in a conditioned place preference assay in mice. Ongoing studies are now investigating circuits in the reward system that underlie PDGFRβ-mediated opioid reward.
The PDGFRβ inhibitor, imatinib, is FDA approved for the treatment of malignancies. Therefore, our work could lead to repurposing imatinib for safer chronic opioid pain therapies and to prevent OUD.
8. Samara Vilca, UMass Chan Medical School, Neurobiology
A Model of Intravenous Fentanyl Self-Administration in C57BL/6J Mice
9. Anusha Bharadwaj, UMass Amherst, Neuroscience
Blood biomarkers and cognitive status in common marmosets
Bharadwaj, A1., Rothwell, E1,2., Freire-Cobo3, Padilla, S4., Hof, P3., Lacreuse, A1,5.
1. Neuroscience and Behavior. University of Massachusetts Amherst
2. Department of Neurobiology, University of Pittsburgh
3. Icahn School of Medicine at Mount Sinai, New York
4. Department of Biology, University of Massachusetts Amherst
5. Psychological and Brain Sciences, University of Massachusetts Amherst
Background
Due to similarities in cognitive and brain function, aging patterns, and the development of various degrees of Alzheimer’s disease (AD)-like neuropathology with age, nonhuman primates (NHPs) are optimal animal models for AD (Shively, Lacreuse, Frye, Rothwell, & Moro, American Journal of Primatology, 2021). The common marmoset (Callithrix jacchus), which has the shortest lifespan of all anthropoids (10-12 years), is a particularly valuable NHP model due to its amenability to longitudinal studies, the manifestation of sex differences in cognitive aging (Rothwell et al., Neurobiology of Aging, 2022) and the development of early AD-like pathology with age (Freire-Cobo et al., Neurobiology of Aging, 2023). The marmoset provides a significant opportunity for the advancement and validation of early biomarkers of AD-like neuropathology. A recent study found that aged marmosets had higher levels of AD-like biomarkers than younger individuals (Phillips et al., Neuroscience Letters, 2024), but did not evaluate cognitive status. In the present study, we examined AD-like biomarkers in a group of male and female marmosets with existing cognitive and neuropathological data.
Method
Blanked blood samples were obtained from a cohort of male and female marmosets (n = 13, age range 6.8-9.36y) with cognitive and neuropathological assessments to evaluate the concentrations of several AD biomarkers and their correlation with cognitive status. The biomarker assays were conducted using the S-PLEX neurology panel 1 kit (NHP) from Mesoscale Discovery (MSD). These kits are specifically designed to detect GFAP, Nfil, and tau concentrations in blood-based samples. Notably, the S-PLEX assays are ultrasensitive, capable of discerning femtogram concentrations of biomarkers in the samples. The S-PLEX assay utilizes electrochemiluminescent methodology, generating light through electrochemiluminescent labels when stimulated by electricity in a suitable chemical environment. Grounded in the principles of the Enzyme-Linked Immunosorbent Assay (ELISA), these assays establish a direct proportionality between the intensity of the emitted light and the amount of analyte present in the sample.
Result
Log-transformed biomarker data were analyzed with separate ANOVAs with Sex and Cognitive Status as factors and Age as a covariate. LogGFAP concentrations were significantly higher in the cognitively impaired compared to the non-impaired animals (F (1, 8) = 15.50, p < .01). Concentrations of the other biomarkers did not differ significantly according to cognitive status. All three biomarkers were influenced by Sex, albeit non-significantly (all ps < .10), suggesting higher levels in males in all cases. A non-significant Sex X Cognitive Status interaction for LogGFAP (F (1, 8) = 4.12, p < .08) suggested that among the impaired group, males had higher levels than females. Preliminary correlation analysis with neuropathological data do not show any significant correlation between blood biomarkers and neuropathology, probably due to small sample size. Analysis with a larger sample size is ongoing.
Conclusion
Alterations in biomarker concentrations act as early signals of cognitive decline, often preceding clinically observable symptoms of AD. Greater blood GFAP, reflecting an inflammatory state, distinguished impaired vs. nonimpaired aged marmosets. Sex influenced all biomarkers concentrations, with higher levels in males. The lack of correlation between blood biomarker and neuropathology will require further validation with a larger number of subjects.
Supported by NIH R01 AG046266 and Sex and Gender in Alzheimer’s SAGA 23 award
10. Caitlyn Edwards, UMass Chan Medical School, Neurobiology
Sex differences in adolescent vs. adult ethanol consumption and subsequent negative affective behavior during forced abstinence
Negative affect experienced during abstinence from alcohol can significantly contribute to relapse and the development of alcohol dependence. Chronic alcohol use during adolescence, in particular, poses a substantial risk for the later development of alcohol use disorder. This study aimed to investigate the voluntary consumption of ethanol and its impact on negative affective behavior, as well as the associated neural changes, in mice that began ethanol consumption during early adolescence (~PND30). Male and female adolescent C57BL/6J mice underwent the Chronic Drinking Forced Abstinence (CDFA) paradigm. In this paradigm, half of the mice (the “Ethanol” group) were given a choice between ethanol and water, while the control mice (the “Water” group) had two bottles containing only water. In Experiment 1, ethanol bottle weights were manually recorded to measure ethanol intake (g/kg/day) and ethanol preference over a six-week period. The bottles were then removed, and two weeks later, the animals underwent several behavioral tests to evaluate negative affect. Although female mice tend to prefer and consume more ethanol than males as adults, we found that male and female mice that began drinking during early adolescence consumed similar levels of ethanol and displayed similar preferences for ethanol over water. Additionally, negative affective behaviors were observed in mice during forced abstinence. In Experiment 2, ethanol intake was assessed using the Lick Instance Quantifier (LIQ) system, which allowed for more precise measurement of ethanol consumption behavior, including lick frequency and duration. Brains were collected at 24 hours and 2 weeks into forced abstinence and analyzed for region-specific changes in whole-brain cFos expression using tissue clearing, whole brain immunostaining, and light sheet microscopy. The adolescent onset of the CDFA model provides a translationally relevant framework for studying negative affect following chronic alcohol consumption and offers insights into the neural circuitry underlying the development of alcohol use disorder.
11. Jingjing Gao, UMass Amherst, Biomedical Engineering
Most disease-modifying treatments for central nervous system (CNS) diseases failed to make it to the market due to poor penetration across the blood-brain barrier (BBB) and side effects. Here we aim to establish the structure-property relationship of nanoparticles in terms of neural cell interactions, brain tissue penetration, and spatial distribution within the brain parenchyma, providing a toolbox for targeted delivery towards pathological regions of the brain, which will be broadly applicable for CNS diseases such as Alzheimer’s disease, Huntington’s disease or Parkinson’s disease.
12. Jennifer Wang, UMass Amherst, Neuroscience
Long-term misalignment of our internal clock and the external day can have significant impacts on neurobehavioral function, including impaired cognitive function and increased risk of developing depression or anxiety. The prefrontal cortex (PFC) is integral to many cognitive and emotional behaviors. Work from our lab reveals that excitatory signaling in layer 2/3 pyramidal neurons in the mPFC is rhythmic at different times of day in a sex-dependent manner. The goal of the present work is to uncover potential molecular signatures that may underlie the observed changes in cellular physiology that are impacted by time of day. Male and female C57BL/6N mice were housed in a 12:12 light/dark cycle. To measure functional changes in the PFC over time of day, spontaneous excitatory postsynaptic currents (sEPSCs) were measured in pyramidal neurons of layers 2/3 using patch-clamp electrophysiology in 8–16-week-old mice at four time bins: ZT0-4, 6-10, 12-16, 18-22. To determine how gene expression related to synaptic transmission changes across the day in the PFC, male and female mice were euthanized at two time points, ZT4 and ZT16. Frozen PFC tissue was collected from each mouse using a coring tool on a cryostat. Total RNA was extracted using an All-Prep Extraction kit. Raw RNA was then processed using a nCounter Neuropathology Panel, and data were analyzed using ROSALIND and Metascape software. Measurements of sEPSCs revealed that ZT12-16 showed higher frequency activity compared to ZT0-4 in males but not females. In contrast, the amplitude of excitatory inputs was not influenced by time of day but was influenced by sex, with females showing higher amplitudes than males. Transcriptomic analysis revealed time-of-day differences in gene expression within the PFC, with genes such as Grim1 and Grik2 (which are essential for glutamatergic signaling in excitatory neurons) showing low expression in the light phase but high expression during the dark. In contrast, Slc1a2, a glutamate transporter gene, showed the opposite effect with higher expression during the light period than the dark period. Together, our data suggests that glutamatergic tone and gene expression within the PFC is heavily time of day dependent, highlighting the importance of time-of-day regulation of excitatory signaling in the PFC.
13. Alex Winsor, UMass Amherst, Organismic & Evolutionary Biology
Many animals use visual information to classify objects into appropriate categories such as food, predators, or social partners. Important questions include whether animals use particular features or combinations of features to identify objects, and where in the brain features are processed. We explore these questions in the modular yet highly integrated visual system of jumping spiders (Araneae: Salticidae). Salticids have six secondary eyes that serve as motion detectors with wide fields of view, and a forward-facing pair of principal eyes capable of high spatial resolution and color vision. The principal-eye retinas have narrow visual fields, but reside at the back of mobile tubes that enable saccades and scanning motions to inspect objects. Together, the two eye types are functionally analogous to our peripheral and foveal vision. In Phidippus audax, we monitored gaze direction using our custom-built eyetracker while simultaneously collecting the first reported dual extracellular recordings of lower and higher-order optic neuropils. We presented spiders with a randomized stimulus set of ecologically relevant holistic objects, including insect prey species, conspecifics, heterospecific salticids, predators, and unpalatable insects, as well as exemplars with stepwise complexity reductions that distill objects into their elemental components, to parse whether spiders respond to local features, global structure, or categories of objects. Our results across nine subjects show that multi-unit activity within both the lower-order (putative principal-eye lamina) and higher-order (putative arcuate body) brain regions are strongly driven by images of palatable prey and suppressed by images of unpalatable prey, even though stimuli within these categories varied widely in appearance. We have begun sorting higher-order single units and detected a ~68% neuronal activation when the spider viewed palatable prey and a ~72% neuronal suppression when the spider viewed unpalatable prey, relative to the baseline firing rate. Moreover, neural responses to reduced images of flies suggest that simple features are extracted for recognition. Ongoing analyses examine responses within stimulus categories and to their simpler components, and correlations between retinal exploration of images (using DeepLabCut) and neural activity. We are now conducting behavioral trials to test if we can predict spider behavioral responses from their neural responses, and we are mapping connectivity of the optic tracts using dextran injections and synapsin immunostaining. In summary, our work reveals neural correlates of prey categorization in an invertebrate predator.
14. Sarah Pallas, UMass Amherst, Neuroscience
The maturation of mammalian sensory cortical networks has generally been ascribed to experience-dependent plasticity: the shaping of neural circuits through sensory inputs during critical periods. In the visual system, dark rearing (DR) disrupts the normal development of neuronal representations of visual space, known as receptive fields (RF), in the primary visual cortex (V1). However, our work suggests that nocturnal or crepuscular mammals develop mature RF properties without visual experience. Hamsters, a crepuscular species, exhibit refined V1 RFs by adolescence even if kept in the dark, but their RFs enlarge in adulthood, implicating a dependence on light for RF development but not for mature RF maintenance (Balmer & Pallas, 2015). This project characterizes V1 RF development in two more species: crepuscular ferrets and nocturnal mice. We hypothesized that ecological niche, rather than phylogenetic relations, determines the need for light exposure in development of RF properties. Nocturnal mice are thus predicted to be independent of light throughout life, but crepuscular ferrets, like hamsters, would build but not maintain their RFs if light-deprived, despite being more genetically distant. Our preliminary data support the hypothesis; ferret RF development and dependence on visual experience is similar to that of hamsters, whereas our data from nocturnal mice suggest that both refinement and maintenance of RFs can occur without visual experience. Our preliminary data support the hypothesis and thus reveal that visual cortical development research on mice is less applicable to humans than research on crepuscular (and perhaps diurnal) mammals. Investigating these differences will help future researchers utilize more appropriate animal models for studying human visual development and disorders.
15. Brendan Philippon, UMass Chan Medical School, Neurobiology
Mechanisms by which DAF-19 regulates functional axon regeneration in C. elegans.
Philippon, Brendan, & Byrne, Alexandra.
Department of Neurobiology, UMass Chan Medical School, Worcester, MA.
Injured motor axons of the central nervous system are incapable of repair, resulting in permanent loss of motor function. Yet axons outside of the brain and spinal cord and in many invertebrate animals are repaired through a process known as functional axon regeneration. Functional axon regeneration includes formation of a growth cone, extension of the axon to its proper target, and reformation of a functional synapse. However, the mechanisms that determine whether an axon is functionally repaired after injury remain unresolved. We recently found that TIR-1/SARM1, a canonical regulator of degeneration, also regulates axon regeneration in C. elegans. TIR-1/SARM1 regulates axon regeneration with the NSY-1/ASK1 p38 MAP kinase pathway and the conserved transcription factor DAF-19/RFX1-3. DAF-19 is expressed broadly in the worm and regulates multiple processes, including ciliogenesis, serotonin biosynthesis, and the innate immune response. We hypothesize the TIR-1 – DAF-19 pathway determines repair by regulating transcription of genes that inhibit or promote axon regeneration. An RNA-seq analysis of daf-19(-), tir-1(-) and daf-19(-); tir-1(-) mutants has revealed DAF-19-dependent changes in gene expression that are critical for functional axon regeneration. Determining how DAF-19 inhibits axon regeneration will further our understanding of how intrinsic regulators of regeneration determine whether an axon repairs itself after injury.
16. Nick Bolden, UMass Chan Medical School, Neurobiology
The initial stages of cocaine addiction are largely mediated by dopaminergic (DAergic) transmission at mesolimbic terminals in the nucleus accumbens (NAc), which signals for strong salient stimuli. Cocaine augments extracellular dopamine (DA) levels by directly inhibiting DA reuptake via the presynaptic DA transporter (DAT), and cocaine’s actions at DATs are required for both contingent and non-contingent cocaine administration in mice. Despite decades of investigation aiming to unravel the mechanisms that impact cocaine reward, it is not well understood how reward perception is modulated in the NAc. Moreover, it is largely unknown whether regulatory mechanisms targeting presynaptic DAergic terminals impact the cocaine reward response. The neuropeptide nociceptin (N/OFQ) is a promising candidate as a potent reward modulator. N/OFQ is expressed throughout the CNS and signals via the Gi/o-coupled nociceptin receptor, NOPR, and previous studies demonstrated that N/OFQ signaling in NAc dampens cocaine-mediated increases in extracellular DA. However, it is unknown whether N/OFQ signaling in NAc similarly dampens cocaine reward, and whether N/OFQ may play a central role in gauging reward perception. Here, we leveraged pharmacological and genetic approaches to directly test whether N/OFQ signaling in NAc alters cocaine reward sensitivity in mice, and whether N/OFQ acts presynaptically on NOPRs in DAergic terminals. N/OFQ infusions into NAc shell (NAcSh) significantly diminished cocaine sensitivity in a conditioned place preference (CPP) assay in females, but had no effect in males. Conditional NOPR silencing in NOPRfl/fl DAergic neurons revealed that presynaptic NOPRs on DAergic terminals were required for cocaine sensitivity changes in response to N/OFQ infusion. Ex vivo slice biotinylation studies in NAc revealed that N/OFQ drove acute increases in DAT surface expression that were similarly dependent upon presynaptic DAergic NOPR expression. Ongoing studies will test whether presynaptic DAergic NOPRs can bi-directionally shift cocaine reward sensitivity and whether NOPR activation in NAcSh alters DA signaling during cocaine CPP, assessed using DA sensors and fiber photometry. Taken together, these findings indicate that N/OFQ robustly influences cocaine reward tone, primarily by acting presynaptically on DAergic terminals. Presynaptic NOPR-mediated DAT regulation further demonstrates that NOPRs on DAergic terminals in NAc are well-positioned to exert significant influence on DA signaling via presynaptic mechanisms.
17. Tsuyoshi Kiniwa, UMass Chan Medical School, Neurobiology
Dissection of the inflammatory milieu at the periventricular region in neurodegeneration diseases
Ependymal cells (EPCs) are ciliated glial cells lining the ventricle surface. Previous work has shown that EPCs are involved in creating cerebrospinal fluid flow and contribute to the etiology of hydrocephalus. However, far less is known about the role of these cells in other brain diseases. Using Multiplexed Error-Robust Fluorescence in situ Hybridization (MERFISH), which allows spatially resolved gene expression profiling with single-cell resolution and immunofluorescence microscopy, we have unexpectedly found that EPCs express high levels of immune-related proteins. This includes the expression of complement protein 3 (C3), a known mediator of synapse elimination in health and disease. Using singe-cell RNA sequencing analysis of the periventricular regions and td-Tomato C3 reporter mouse, we confirmed C3 expression of the EPCs and its upregulation during neuroinflammation. At the same time, we also observed the nuclear translocation of signal transducer and activator of transcription 3 (STAT3), major immunological signaling molecules, are increased in EPCs. This increase in EPC inflammatory signaling is also accompanied by an enrichment of reactive microglia and astrocytes around the ventricles. We are now investigating how this inflammatory signaling in EPCs contributes to neuroinflammation throughout the brain and is involved in the pathogenesis of neurodegenerative disease.
18. Chun-Wei Chen, UMass Chan Medical School, Neurobiology
Neuronal subtype vulnerability to microglial-induced synapse loss in neuroinflammation
Rebecca Beiter1*, Chun-Wei Chen1,2*, Ruixuan Xiao1,2*, Dorothy P. Schafer1
1 Department of Neurobiology, Brudnick Neuropsychiatric Research Institute, UMass Chan Medical School, Worcester, MA, USA
2 Morningside Graduate School of Biomedical Sciences, UMass Chan Medical School, Worcester, MA, USA
*These authors contributed equally to this work
Microglia, the professional phagocytes of the brain, are known to play an important role in shaping neuronal circuitry by engulfing synapses during development. Microglia have also been shown to engulf synapses in multiple neurodegenerative conditions, including Alzheimer’s Disease, Huntington’s disease, and multiple sclerosis (MS). However, unlike development, this engulfment of synapses during disease has been shown to result in both cognitive and physical impairments. Recently, work using experimental autoimmune encephalomyelitis (EAE), an animal model of MS, demonstrated that, in the context of neurodegeneration, microglia engulf synapses from retinal ganglion cells (RGCs) that project into the thalamus, resulting in visual impairment. This engulfment is driven by deposition of the complement component C3 on synapses. However, it remains unclear why some synapses are tagged for removal while others are spared. In this work, we have utilized the known molecular heterogeneity of RGCs to determine whether specific subtypes of neurons are more vulnerable to neuroinflammation-related synapse loss than others. We have demonstrated that microglia preferentially engulf synapses from αRGCs, a subtype of RGC characterized by a large cell body, compared to other subtypes of RGCs. We are currently using this data to identify neuron-specific transcriptional programs that may increase vulnerability to synapse loss. This data will allow us to further dissect the mechanisms driving synapse loss in neuroinflammation and will provide potential therapeutic targets for slowing detrimental synapse loss.
19. Travis Faust, UMass Chan Medical School, Neurobiology
Synapses remodel in response to changes in sensory experience and neural activity. Microglia and astrocytes both contribute to activity-dependent synapse remodeling by removing synapses from less active neurons. Yet, how microglia and astrocytes communicate to remodel synapses remains an open question. Previously, our lab showed that microglia engulf and remove synapses in neonate mouse barrel cortex following whisker lesioning and whisker trimming-induced reductions of neural activity. Whisker lesioning-induced synapse removal was dependent on signaling between neuronal fractalkine (CX3CL1) and its cognate microglial fractalkine receptor (CX3CR1). Using this whisker lesioning paradigm, I explored how astrocytes and microglia coordinate to regulate synapse remodeling. Using translating ribosome affinity purification followed by RNA-seq (TRAP-seq) and MERFISH spatial transcriptomics, I identified novel Wnt-dependent receptor-ligand signaling between microglia and astrocytes that drives synapse remodeling. Intriguingly, microglia-to-astrocyte Wnt signaling is CX3CR1-CX3CL1 signaling dependent and induces reduced astrocyte-synapse contact prior to synapse engulfment by microglia. I propose that astrocyte process retraction facilitates microglial engulfment by altering synaptic properties and increasing synapse availability. Together, my results identify a novel mechanism by which microglia signal to astrocytes to facilitate synapse engulfment and remodeling of cortical synapses in response to changes in sensory experience. As changes in astrocyte-synapse contact occur naturally during sleep, as circuits mature, and in an array of neurological disorders, I propose that astrocyte-synapse contact could be a general regulator of microglial synapse engulfment and subsequent synapse remodeling. I am now actively exploring this possibility by examining how other manipulations that affect astrocyte-synapse contact impact developmental critical windows.
20. Wenjia Huang, UMass Chan Medical School, Neurobiology
After neuronal injury, damaged axons need to first regenerate and then reform synapses with appropriate postsynaptic cells to regain function. However, a comprehensive molecular and cellular understanding of how functional axon regeneration is regulated remains elusive. From a candidate screen in Caenorhabditis elegans, we found that CLA-1/Clarinet/Piccolo, a highly conserved presynaptic scaffolding protein, is a powerful inhibitor of functional axon regeneration in GABA motor neurons. Injured axons in cla-1(-) mutants regenerate more frequently and further compared to injured wild-type axons. Surprisingly, despite the well characterized function of CLA-1 and its orthologs Piccolo and Fife in synaptic vesicle clustering and release at the active zone, regenerated axons in cla-1(-) mutants also regain more motor function than injured wild-type axons.
We asked whether inhibiting axon regeneration is a shared function of scaffolding proteins by screening a panel of synaptic gene mutants for their ability to inhibit axon regeneration. We found that in contrast to the enhanced axon regeneration observed in cla-1 mutants, injured axons lacking the scaffolding gene elks-1/ELKS regenerate as frequently as wild-type axons. Therefore, inhibiting axon regeneration is not a shared consequence of disrupting active zone scaffolding proteins. In contrast, disrupting unc-13, a core presynaptic exocytosis gene, robustly inhibited axon regeneration, as observed for its mammalian homolog MUNC13 (Hilton et al.,2022). The amount of function that is disrupted by cla-1(-) and unc-13(-) mutations differs significantly; however, we observed a similar increase in axon regeneration in unc-13(-) and cla-1(-) single mutants, suggesting the ability of CLA-1 to inhibit axon regeneration is not correlated with the magnitude of its contribution to synaptic function. Finally, we observed an additive increase of axon regeneration in unc-13(-);cla-1(-) double mutants compared to either single mutant, indicating active zone proteins CLA-1 and UNC-13 inhibit axon regeneration through independent mechanisms. Together, these data reveal CLA-1 likely inhibits axon regeneration independently of its role at the synapse, using a previously unidentified mechanism.
We addressed the critical question of how CLA-1 inhibits functional regeneration with a combination of biochemical, genetic, and molecular approaches. Our findings have revealed the tissue in which CLA-1 acts during axon regeneration, how it responds to axon injury spatiotemporally, and the downstream molecular and cellular signaling pathways that mediate its role in regeneration. Our results add significantly to our understanding of the injury response and suggest decreasing CLA-1/Piccolo function is a promising strategy to promote axon regeneration without impairing the synaptic function of regenerated axons.
21. Emily Naughton, UMass Amherst, Neuroscience
In periods of rapid growth and development, myelin-producing glial cells (oligodendrocytes, OLs) wrap lipid-rich myelin segments around axons, supporting fast communication across brain regions. White matter increases in frontotemporal brain regions during adolescence, corresponding with improvements in executive functioning, complex cognitive processing, and stress regulation. These functions are impacted early-on in degenerative diseases like Frontotemporal Dementia and Alzheimer’s Disease, suggesting that the integrity of white matter tracts interconnecting these regions may be impaired. It is therefore important to better understand the cellular dynamics of OLs during adolescence and adulthood, including the temporal and spatial patterns of new OL and myelin formation during these developmental periods. A major challenge in the field has been visualizing and tracking de novo myelin sheath formation. Herein we have successfully distinguished between new and previously formed myelin using a double transgenic conditional mouse reporter line (NG2-CreER:Tau-mGFP). By combining this approach with triple immunofluorescent labeling and confocal microscopy, we have visualized the rapid differentiation of OLs and formation of new myelin throughout frontotemporal white matter regions in adolescent mice, including the anterior commissure, forceps minor of the corpus callosum, and the white matter tracts of the hippocampus and amygdala. Using CLARITY and light-sheet microscopy, we have also generated a 3D map of myelinated tracts formed during adolescence that remain in these regions well into adulthood. The cellular dynamics of OLs may change across the lifespan and affect myelin maintenance and the function of these frontotemporal circuits, leaving these pathways susceptible to degeneration. These findings could therefore have significant implications for identifying targets and timelines of therapeutic intervention as individuals age.
22. Travis Hodges, Mount Holyoke College, Psychology & Education + Neuroscience
Title: Adolescent social instability stress affects cognitive bias and other depressive behaviors in male and female rats across the lifespan
Authors: Annabeth Loftman, Angelina Amato, Persephone Gu, Callie Ten Kate, Shanshan Zhu, Juddy Nam, Travis E. Hodges
Abstract: Negative cognitive bias is a symptom of depression and cognitive symptoms of depression are more severe in females than in males. Social instability stress (SS) induces depressive-like behavior in rats, but on one has studied the effects of SS on cognitive bias. Here, we examined the effect of SS during adolescence on cognitive bias from adolescence to young adulthood (group 1) and from young adulthood to middle-age (group 2) in male and female rats. SS impaired social interaction in all rats. In group 1, adolescent female SS rats displayed more passive coping (freezing) and less active coping (avoidance) than same-sex controls, and female rats displayed a more negative cognitive bias than same-age males in adulthood. In group 2, SS increased negative cognitive bias regardless of age, and female rats displayed more active coping than male rats. Open field and anhedonia were also examined and compared to cognitive bias results. All in all, adolescent social stress might affect the cognitive bias of females earlier than males.
23. Grace Simpson, Mount Holyoke College, Neuroscience and Psychology
Title: The effect of methylazoxymethanol acetate (MAM) on neurogenesis and cognitive bias in male and female rats
Authors: Emily Steadman, Grace Simpson, Manuela Ribas, Travis E. Hodges
Abstract: Negative cognitive bias, the interpretation of ambiguous stimuli as negative, is present in individuals with major depressive disorder. Studies have found a greater effect of hippocampal neurogenesis on the cognitive bias of male rats than female rats, such that increased neurogenesis is negatively correlated with negative cognitive bias in males, no effect found in females. Here, male and female Long-Evans rats underwent chronic unpredictable stress or no stress, and then stressed rats were injected with either saline or the neurogenesis inhibitor methylazoxymethanol acetate (MAM) before we examined their cognitive bias. Brains were collected, and both doublecortin and Ki67 were examined. We predicted that stressed male rats injected with MAM would display a more positive cognitive bias than saline-injected stressed males, and we predicted little effect in female rats. With these data, we aim to discover whether inhibiting hippocampal neurogenesis could help improve positive cognitive bias in a sex-specific manner.
24. Rebecca Pavchinskiy, UMass Chan Medical School, Neurobiology
Anxiety disorders affect ~31% of U.S. adults in their lifetime. Aberrant fear processing where non-fearful stimuli triggers fear behavior contributes to anxiety. Fear perception and response are critical behaviors driven by intrinsic neural networks. Elucidating potentially threatening stimuli as non-fearful triggers habituation to fear and is an imperative survival instinct. However, specific brain circuitry driving inhibitory learning of fear responses are not fully elucidated. Moreover, behavioral paradigms assessing fear learning without utilizing pain, i.e. foot shock, are underexplored. To assess behavioral habituation to psychological threat, we developed a multi-day visual looming stimulus (VLS) paradigm where mice receive 5 presentations of an overhead loom stimulus, mimicking a bird of prey, for 3 days. The looming apparatus contained a lowered shelter across from an overhead monitor which displayed the looming stimulus, consisting of 15 repetitions of an expanding circle (250 ms expansion, 250 ms hold, and 500 ms pause per repetition). In response to the first looming trial, we observed multiple fear associated behaviors including freezing, fleeing, and tail rattling. Mice displayed robust freezing during the initial looming trial which significantly decreased, eventually returning near pre-loom baseline by the third day. Time spent in shelter following stimulus presentation decreased on the second and third day when compared to Day 1. Interestingly, tail rattle responses were abolished following Day 1 of the VLS paradigm. More detailed analysis within Day 1 looming revealed a behavioral shift from freeze to delayed flee between the first and fifth trial of Day 1 VLS marking a shift in threat perception. Together, these results establish multi-day VLS as a non-Pavlovian fear learning model to help identify novel neurocircuitry underlying inhibition of fear responses to naturalistic threats.
25. Max Zinter, UMass Chan Medical School, Neurobiology
Mbnl1, an RNA splicing factor, associates with the arc capsid in an activity-dependent manner
26. Anita Khasnavis, UMass Chan Medical School, Neurobiology
Opioids are the gold-standard treatment for severe pain, yet their repeated administration can yield numerous adverse consequences. Long-term opioid use leads to analgesic tolerance which requires increased dose to overcome reduced analgesia, heightening the risk of centrally-mediated side effects such as respiratory depression, addiction, and overdose. Peripheral opioids offer a safer alternative as they avoid CNS penetration, but repeated administration still results in tolerance and lowers their efficacy.
Previous findings show that spinal tolerance is regulated by the platelet-derived growth factor receptor beta (PDGFR), which is recruited upon -opioid receptor (MOPr) activation by opioids, via the release of the platelet-derived growth factor-B (PDGF-B) ligand. Accordingly, spinal inhibition of PDGFR or of PDGF-B prevents spinal tolerance. Peripherally, the mechanisms of tolerance remain unknown. Skin keratinocytes have been shown to express MOPr and PDGF-B, while skin nerve endings of peripheral sensory neurons (PSNs) express PDGFR. Keratinocytes are known to communicate with PSNs to transduce somatosensory information, and this communication is hypothesized to be mediated via keratinocyte-released factors. We hypothesize that peripheral inhibition of PDGFR signaling will block opioid-induced peripheral tolerance.
To test our hypothesis, we developed a model for peripheral tolerance, induced by 5-day repeated intraplantar (i.pl.) administration of morphine in mice. We found that this peripheral tolerance was prevented by either blocking PDGFR with imatinib or with a selective PDGFR monoclonal antibody. We also found that scavenging the PDGF-B ligand blocked peripheral tolerance, and repeated peripheral injections of PDGF-B are sufficient to cause peripheral tolerance. Additionally, keratinocytes from animals peripherally tolerant to morphine had an increase in PDGF-B expression in MOPr positive keratinocytes compared to their saline-injected counterparts. We also used optogenetics to selectively activate keratinocytes in mice expressing channelrhodopsin2 in their keratinocytes (Kr14-ChR2). We found that repeated keratinocyte activation for five days results in peripheral tolerance to morphine in opioid naïve mice, suggesting that keratinocyte stimulation is sufficient to cause peripheral morphine tolerance. Taken together, these results indicate that PDGFR and its ligand PDGF-B are necessary and sufficient for peripheral tolerance, and that keratinocytes could be the source of PDGF-B required to mediate peripheral tolerance after activation by opioids.
27. Ellen Rodberg, UMass Amherst, Neuroscience
Locus coeruleus (LC) neurons are intimately connected with diverse brain functions, most prominently attention, arousal, stress responses, and cognition. Published studies of LC activity cover many traits (species, sex, etc.) but rely on small sample sizes (usually tens of neurons), which has precluded a systematic and robust assessment of how these features affect LC activity. Here, we leverage a pooled dataset of 1,855 single units from 20 laboratories to comprehensively compare LC activity. Verified LC activity was recorded from deafferenated brain slices and intact animals during wakefulness or under different anesthetics. Samples included male non-human primates and rats and mice of both sexes. In some cases, LC activity was recorded from disease models and cell-type selective genetic modifications. We used a negative binomial regression model to identify the individual and combined effects of various attributes on firing rate. This powerful analysis revealed important species-, sex-, age-, and disease model-specific activity. Lastly, in contrast to the foundational concept of two-mode (tonic-phasic) LC activity, we discovered multiple bursting sub-modes and complex second order spike train patterns associated with different LC preparations. In sum, inherent differences in LC activity result from species-, age- and sex-dependent factors. Our findings offer insight into why LC-dependent behavioral and cognitive functions depend on sex and age and may help explain the known association of sex and age with psychiatric disorders.
28. Timmy Le, UMass Chan Medical School, Neurobiology
In the nucleus accumbens (NAc), a brain region known for its role in reward, medium spiny neurons (MSNs) receive glutamatergic inputs from the medial prefrontal cortex (mPFC) and the basolateral amygdala (BLA), two brain regions implicated in mediating alcohol’s effects. Previously, we reported that, in 8-week-old male mice, mPFC and BLA inputs synapse onto the same MSNs where they reciprocally inhibit each other pre-synaptically in a strict time-dependent manner, a phenomenon called synaptic gating. However, the influence of sex and age on synaptic gating, and its sensitivity to binge alcohol drinking, remained unknown. To address these key biological questions, we performed whole-cell recordings in NAc MSNs and optogenetically evoked BLA- and mPFC-EPSPs in 6-, 8-, and 12-week-old male and female mice. We found that, in alcohol naïve males, the ability of cortical inputs to inhibit the transmission of information from the BLA region increases significantly in 8 weeks old mice compared to younger (6-week-old) and older (12-week-old) animals, an effect not observed in females. Regarding the influence of sexes, mPFC gating of BLA synaptic transmission was significantly stronger in 8-week-old males compared to females of the same age, a difference that disappeared in 12-week-old mice. Interestingly, binge alcohol drinking negates the observed synaptic gating age difference. Overall, our results show that age and sex influence how NAc MSNs process cortical and amygdala information through synaptic gating, a phenomenon disrupted by binge alcohol drinking in an age-dependent manner.
29. Haley Melikian, UMass Chan Medical School, Neurobiology
The initial stages of cocaine addiction are largely mediated by dopaminergic (DAergic) transmission at mesolimbic terminals in the nucleus accumbens (NAc), which signals for strong salient stimuli. Cocaine augments extracellular dopamine (DA) levels by directly inhibiting DA reuptake via the presynaptic DA transporter (DAT), and cocaine’s actions at DATs are required for both contingent and non-contingent cocaine responses in mice. Despite decades of investigation aiming to unravel the mechanisms that impact cocaine reward, it is not well understood how reward perception is modulated in the NAc. Moreover, it is largely unknown whether regulatory mechanisms targeting presynaptic DAergic terminals impact the cocaine reward response. The neuropeptide nociceptin (N/OFQ) is a promising candidate as a potent reward modulator. N/OFQ is expressed pan-neuronally and signals via the Gi/o-coupled nociceptin receptor, NOPR. Previous studies demonstrated that N/OFQ signaling in NAc dampens acute DA increases in response to systemic cocaine injection. However, it is unknown whether N/OFQ signaling in NAc similarly dampens cocaine reward. Here, we leveraged pharmacological and genetic approaches to directly test whether N/OFQ signaling in NAc alters cocaine reward sensitivity in mice, and whether N/OFQ acts presynaptically on NOPRs in DAergic terminals. N/OFQ infusions into NAc shell (NAcSh) significantly diminished cocaine sensitivity in a conditioned place preference (CPP) assay in females, but had no effect in males. Conditional NOPR silencing in NOPRfl/fl DAergic neurons revealed that presynaptic NOPRs on DAergic terminals were required for the cocaine sensitivity changes in females. Ex vivo slice biotinylation studies in NAc revealed that N/OFQ drove acute increases in DAT surface expression that were similarly dependent upon presynaptic DAergic NOPR expression. Ongoing studies will test whether presynaptic DAergic NOPRs can bi-directionally shift cocaine reward sensitivity and whether NOPR activation in NAcSh alters DA signaling during cocaine CPP, assessed using DA sensors and fiber photometry. Taken together, these findings indicate that N/OFQ robustly influences cocaine reward tone, primarily by acting presynaptically on DAergic terminals. Presynaptic NOPR-mediated DAT regulation further demonstrates that NOPRs on DAergic terminals in NAc are well-positioned to exert significant influence on DA signaling via presynaptic mechanisms.
30. Eli Min, UMass Chan Medical School, Neurobiology
Neuronal injury often leads to long-term disability because many neurons, such as those in the central nervous system, are unable to repair themselves. Significant effort has focused on identifying intrinsic mechanisms that can be manipulated to initiate a form of repair called axon regeneration; however, even when mammalian axons are manipulated to regenerate, they are frequently misguided, preventing them from reestablishing functional interactions with the appropriate cells. Our current understanding of axon guidance is restricted almost exclusively to the uninjured developing nervous system; therefore, a better understanding of the cellular and molecular mechanisms that guide axons in adults is urgently needed to repair the mature nervous system. Intriguingly, injured C. elegans motor axons successfully regenerate along a similar path as developing axons. This ability inspired a candidate screen for molecules that, when absent, result in misguided regenerating axons. We identified an extracellular matrix protein (ECM) and its binding partners that guide regenerating motor axons specifically in the adult nervous system and are required to restore function to the injured nervous system. Our new understanding of how the identified ECM complex functions specifically in the post-developmental nervous system to guide regenerating motor axons and promote functional repair will significantly improve our understanding of axon guidance and the injury response.
31. Chris Perk, UMass Amherst, Neuroscience
Role of rat frontal association area in response inhibition during a novel GoNoGo task
Christopher G. Perk, Iván García Álvarez, and David E. Moorman
The prefrontal cortex is well known to be involved in executive function, including appetitive conditioning, response inhibition, and goal-directed action selection. However, the role of the frontal association area (FrA, the most anterior part of this region in rodents) in executive function has not been well characterized. To investigate the involvement of FrA in response inhibition we bilaterally injected an adeno-associated virus containing inhibitory Designer Receptors Activated Only by Designer Drugs (DREADDs) into the FrA of adult Long-Evans rats (n = 13, 150 or 300 nl/hemisphere) and implanted a stimulating electrode onto the right median forebrain bundle (MFB, to enable intra-cranial self-stimulation behavior), before training them on a Go-NoGo task.
Go No-Go task training was performed in an operant chamber containing 2 nose-pokes, each positioned on the left and right side of one wall. During Go trials animals were required to enter the left nose-poke when illuminated, which produced a 500 ms tone cue (1kHz). Rats were then required to hold the nose-poke for the duration of the cue, immediately after which the light was extinguished, and the right nose-poke was illuminated. Rats received MBF stimulation, accompanied by three tone pips (100ms each, 2.5kHz), if they entered the right nose-poke within 2s of it becoming illuminated. During No-Go trials, rats were required to enter the illuminated left nose-poke immediately after which a unique 500ms cue tone (3.5kHz) indicated that they needed to hold for an additional 500ms after the termination of the compound tone/light cue to receive MFB stimulation and tone pips. For fully trained animals (> 75% accuracy on both trial types) all sessions were 1h in duration. Animals were initially trained on a 50Go:50NoGo schedule and after deschloroclozapine (DCZ, 0.1mg/kg, i.p., DREADD ligand) and dimethyl sulfoxide (DMSO, vehicle) challenges were retrained and retested on 80Go:20NoGo and 20Go:80NoGo ratios.
We found DREADD-mediated inhibition of the FrA increased Go trial hold times vs. vehicle (p=0.0197), but only in animals on the 50Go:50NoGo schedule. This suggests a role for FrA in sensory-motor timing with respect to the instructional Go cue when uncertainty, and thus attentional requirements, were likely highest. We also observed an increased number of inter-trial interval entries into the hold/trial initiation nose-poke (p=0.0497) suggesting heightened impulsivity with regards to trial initiation.
32. Lauren O’Connor, UMass Chan Medical School, Neurobiology
Neurodegeneration results in a devastating loss of cognitive and motor abilities for which there is a critical lack of therapeutic approaches. A greater understanding of the genetic and cellular mechanisms that regulate degeneration is critical to developing effective therapies. Emerging evidence suggests the microbiome plays an important role in many physiological processes including the onset and progression of neurodegenerative diseases. The well characterized nervous system, conserved molecular mechanisms of degeneration, and the ability to exist on a uni-bacterial diet, make <i>C. elegans</i> a highly tractable model to dissect the effects of diet and the microbiome on degeneration. We developed a new model of motor neuron degeneration to readily screen for neuroprotective bacterial diets, neuroprotective molecules, and metabolites. The screen revealed a number of bacteria that significantly protect motor neurons from degenerating compared to the standard <i>E. coli</i> OP50 diet. Using detailed genetic analyses, along with high-performance liquid chromatography-mass spectrometry, we have identified neuroprotective metabolites that are produced by the identified bacteria, enzymes that function within the intestine to digest these metabolites, and resulting protective changes in neuronal gene expression. Identifying neuroprotective bacteria and the mechanisms by which they exert protection provides a greater understanding of ‘gut-brain’ interactions and how they can be manipulated to protect the nervous system.
33. Korey Sudana, UMass Amherst, Neuroscience
The maturation of mammalian sensory cortical networks has generally been ascribed to experience-dependent plasticity: the shaping of neural circuits through sensory inputs during critical periods. In the visual system, dark rearing (DR) disrupts the normal development of neuronal representations of visual space, known as receptive ¬fields (RF), in the primary visual cortex (V1). However, our work suggests that nocturnal or crepuscular mammals develop mature RF properties without visual experience. Hamsters, a crepuscular species, exhibit refined V1 RFs by adolescence even if kept in the dark, but their RFs enlarge in adulthood, implicating a dependence on light for RF development but not for mature RF maintenance (Balmer & Pallas, 2015). This project characterizes V1 RF development in two more species: crepuscular ferrets and nocturnal mice. We hypothesized that ecological niche, rather than phylogenetic relations, determines the need for light exposure in development of RF properties. Nocturnal mice are thus predicted to be independent of light throughout life, but crepuscular ferrets, like hamsters, would build but not maintain their RFs if light-deprived, despite being more genetically distant. Our preliminary data support the hypothesis; ferret RF development and dependence on visual experience is similar to that of hamsters, whereas our data from nocturnal mice suggest that both re¬finement and maintenance of RFs can occur without visual experience. Our preliminary data support the hypothesis and thus reveal that visual cortical development research on mice is less applicable to humans than research on crepuscular (and perhaps diurnal) mammals. Investigating these differences will help future researchers utilize more appropriate animal models for studying human visual development and disorders.
34. Olga Revka, UMass Amherst, Neuroscience
A history of excessive alcohol use increases the risk of Alzheimer’s related dementia (ARD), particularly early onset dementia in humans. Stress is independently a risk factor for ARD and a known promoter of excessive alcohol use. Understanding the role that excessive alcohol history and stress play in the development of changes in cognition and neural function relevant to ARD may identify therapeutic targets to manage risk. The goal of the current study was to investigate mid-life cognition and related changes in vulnerable brain regions after chronic alcohol and stress.
Three-month-old male and female C57BL/6 mice were given access to ethanol (15%, v/v) 1 hr per day in their homecage to establish baseline drinking. Subsequently, mice underwent four cycles of alternating chronic intermittent ethanol (CIE) vapor exposure (1 week) and repeated forced swim stress (FSS) (1 week), with control groups exposed to Air and no stress. Animals then remained abstinent for 5 months in their homecage. At middle age (11 months), mice received 1 week access to homecage alcohol (15%, 1hr/day) followed by a final CIE/FSS. Following this, they performed a spatial memory based Barnes maze test and reversal. Brains were collected for RNAscope and IHC assays to evaluate relevant pathological changes.
The Barnes maze revealed statistically significant differences between heavy drinkers in the CIE/FSS and low drinking control Air/NS animals. High drinking CIE/FSS mice showed several impairments during the reversal challenge of the Barnes maze. CIE/FSS showed increased primary latency and number of errors during the reversal test compared to the test. Furthermore CIE/FSS mice demonstrated a reduced time in the target quadrant during the reversal test compared to Air/NS. In addition to the behavior test, markers of autophagy, oxidative stress, and apoptosis in locus coeruleus were evaluated.
Our results indicate that a history of excessive alcohol and stress significantly impairs cognitive flexibility and various aspects of memory. The dysfunction in locus coeruleus may be part of this process that links alcohol use with ARD. These findings provide insights for future diagnostics and prevention of Alzheimer’s disease in relation to alcohol use disorder.
35. Wouter Hoogkamer, UMass Amherst, Kinesiology
The Human Robotic Systems Laboratory (Meghan Huber, MIE), the Movement Neuroscience Laboratory (Douglas Martini, KIN) and the Integrative Locomotion Laboratory (Wouter Hoogkamer, KIN) have developed several protocols and devices to study and improve neural adaptation of gait in aging and neurological populations. This innovative approach to gait rehabilitation is grounded in neurophysiology, motor control and robotics, leveraging multidisciplinary expertise to improve rehabilitation efficacy. The impact of this research is both immediate and protracted. The immediate impact establishes the foundation for robotic assisted gait rehabilitation duration and magnitude, with a protracted impact rooted in the versatility and generalizability of the gait rehabilitation approach. The long-term goal of this research is to identify changes in fall risk earlier to allow for earlier and more efficacious interventions.