Biology subjects

Gilpin, N. W.

Publications and source records attributed to Gilpin, N. W..

10 recordsLinked to original sources

bioRxiv2025

Alcohol Attenuates CRF-Induced Excitatory Effects from the Extended Amygdala to Dorsostriatal Cholinergic Interneurons

Alcohol relapse is associated with corticotropin-releasing factor (CRF) signaling and altered reward pathway function, though the precise mechanisms remain unclear. Here, we investigated how CRF modulates cholinergic interneurons (CINs) in the dorsal striatum, a region critical in mediating cognitive flexibility and action selection. Using monosynaptic and retrograde circuit tracing, we identified direct inputs from CRF-expressing (CRF) neurons in the central amygdala (CeA) and bed nucleus of the stria terminalis (BNST) to dorsal striatal CINs. We showed that CINs express CRF receptor 1 (CRFR1) and established their functional connectivity with CeA/BNST CRF projections. Functional recordings revealed that CRF enhanced CIN excitability and promoted acetylcholine release in the dorsal striatum. However, acute alcohol exposure and withdrawal attenuated the excitatory effect of CRF on CIN firing, suggesting a mechanism by which alcohol disrupts CRF-dependent neuromodulation. These findings reveal a previously unrecognized CRF-CIN pathway linking the extended amygdala to the dorsal striatum and provide new insight into how CRF and alcohol interact to impair striatal function. This work highlights CRF signaling as a potential target for understanding stress-induced changes to the reward pathway. HighlightsO_LIDorsal striatal CINs receive monosynaptic CRF+ inputs from CeA and BNST neurons. C_LIO_LICRFR1 is expressed in striatal CINs, and CRF+ fibers are present in the dorsal striatum. C_LIO_LICRF enhances dorsal striatal CIN activity via CRFR1 signaling. C_LIO_LIAcute alcohol exposure impairs CRF-induced cholinergic activity. C_LI Significance StatementThe dorsal striatum regulates goal-directed behavior and is implicated in alcohol use disorder (AUD). Within this region, cholinergic interneurons (CINs) support cognitive flexibility and receive input from limbic areas, including the central amygdala (CeA) and bed nucleus of the stria terminalis (BNST). In this study, we identified direct projections from CRF-producing neurons in the CeA and BNST to dorsal striatal CINs, a subset of which express CRF receptor 1 (CRFR1). Electrophysiological recordings confirmed these projections provide functional input that is disrupted by acute alcohol exposure. These findings lay the groundwork for future studies on how CRF and alcohol interact to impair striatal function.

neuroscience↗

bioRxiv2024

Histological comparison of repeated mild weight drop and lateral fluid percussion injury models of traumatic brain injury (TBI) in female and male rats.

Traumatic brain injury (TBI) heterogeneity has led to the development of several preclinical models, each modeling a distinct subset of outcomes. Selection of an injury model should be guided by the research question and the specific outcome measures of interest. Consequently, there is a need for conducting direct comparisons of different TBI models. Here, we used immunohistochemistry to directly compare the outcomes from two common models, lateral fluid percussion (LFP) and repeat mild weight drop (rmWD), on neuropathology in adult female and male Wistar rats. Specifically, we used immunohistochemistry to measure the effects of LFP and rmWD on cerebrovascular and tight junction disruption, inflammatory markers, mature neurons and perineuronal nets in the cortical site of injury, cortex adjacent to injury, dentate gyrus, and the CA2/3 area of the hippocampus. Animals were randomized into either LFP or rmWD groups. The LFP group received a craniotomy prior to LFP (or corresponding sham procedure) three days later, while rmWD animals underwent either weight drop or sham (isoflurane only) on each of those four days. After a recovery period of 7 days, animals were euthanized, and brains were harvested for analysis of RECA-1, claudin-5, GFAP, Iba-1, CD-68, NeuN, and wisteria floribunda lectin. Overall, our observations revealed that the most significant disruptions were evident in response to LFP, followed by craniotomy-only, while rmWD animals showed the least residual changes compared to isoflurane-only controls. These findings support consideration of rmWD as a mild, transient injury. LFP leads to longer-lasting disruptions that are more closely associated with a moderate TBI. We further show that both craniotomy and LFP produced greater disruptions in females relative to males at 7 days post-injury. These findings support the inclusion of a time-matched experimentally-naive or anesthesia-only control group in preclinical TBI research to enhance the validity of data interpretation and conclusions.

neuroscience↗

bioRxiv2023

JZL184 increases anxiety-like behavior and does not reduce alcohol consumption in female rats after repeated mild traumatic brain injury.

Alcohol use disorder (AUD) is highly comorbid with traumatic brain injury (TBI). Previously, using a lateral fluid percussion model (LFP) (an open model of head injury) to generate a single mild to moderate traumatic brain injury (TBI), we showed that TBI produces escalation in alcohol drinking, that alcohol exposure negatively impacts TBI outcomes, and that the endocannabinoid degradation inhibitor (JZL184) confers significant protection from behavioral and neuropathological outcomes in male rodents. In the present study, we used a weight drop model (a closed model of head injury) to produce a repeated mild TBI (rmTBI, 3 TBIs, spaced by 24 hours) to examine the sex-specific effects on alcohol consumption and anxiety-like behavior in rats, and whether systemic treatment with JZL184 would reverse TBI effects on those behaviors in both sexes. In two separate studies, adult male and female Wistar rats were subjected to rmTBI or sham using the weight drop model. Physiological measures of injury severity were collected from all animals. Animals in both studies were allowed to consume alcohol using an intermittent 2-bottle choice procedure (12 pre-TBI sessions and 12 post-TBI sessions). Neurological severity and neurobehavioral scores (NSS and NBS, respectively) were tested 24 hours after the final injury. Anxiety-like behavior was tested at 37-38 days post-injury in Study 1, and 6-8 days post-injury in Study 2. Our results show that females exhibited reduced respiratory rates relative to males with no significant differences between Sham and rmTBI, no effect of rmTBI or sex on righting reflex, and increased neurological deficits in rmTBI groups in both studies. In Study 1, rmTBI increased alcohol consumption in female but not male rats. Male rats consistently exhibited higher levels of anxiety-like behavior than females. rmTBI did not affect anxiety-like behavior 37-38 days post-injury. In Study 2, rmTBI once again increased alcohol consumption in female but not male rats, and repeated systemic treatment with JZL184 did not affect alcohol consumption. Also in Study 2, rmTBI increased anxiety-like behavior in males but not females and repeated systemic treatment with JZL184 produced an unexpected increase in anxiety-like behavior 6-8 days post-injury. In summary, rmTBI increased alcohol consumption in female rats, systemic JZL184 treatment did not alter alcohol consumption, and both rmTBI and sub-chronic systemic JZL184 treatment increased anxiety-like behavior 6-8 days post-injury in males but not females, highlighting robust sex differences in rmTBI effects.

neuroscience↗

bioRxiv2023

Sex differences in cocaine self-administration by Wistar rats after predator odor exposure

Traumatic stress disorders are defined in part by persistent avoidance of trauma-related contexts. Our lab uses a preclinical model of traumatic stress using predator odor (i.e., bobcat urine) in which some but not all rats exhibit persistent avoidance of odor-paired stimuli, similar to what is seen in humans. Bobcat urine exposure increases alcohol consumption in male Avoider rats, but it has not been tested for its effects on intake of other drugs. Here, we tested the effect of bobcat urine exposure on cocaine self-administration in adult male and female Wistar rats. We did not observe any effect of bobcat urine exposure on cocaine self-administration in male or female rats. We observed that (1) female rats with long access (6 hours) to cocaine self-administer more cocaine than long-access males, (2) long-access males and females exhibit escalation of cocaine intake over time, (3) stressed rats gain less weight than unstressed rats following acute predator odor exposure, (4) baseline cocaine self-administration is predictive of subsequent cocaine self-administration. The results of this study may inform future work on predator odor effects on cocaine self-administration.

animal behavior and cognition↗

bioRxiv2021

Chronic THC vapor rescues inflammation-related thermal hyperalgesia and causes cell type-specific modifications in vlPAG neurons

AbstractIn an effort to reduce reliance on opioids for the treatment of pain in the clinic, ongoing work is testing the utility of cannabinoid drugs as a potential alternative for treatment of chronic pain. We tested chronic THC vapor inhalation effects on thermal nociception and mechanical sensitivity, as well as midbrain (i.e., ventrolateral periaqueductal gray [vlPAG]) neuronal function, in adult male and female Wistar rats with chronic inflammatory pain (CFA treatment). We report that chronic THC vapor inhalation rescues both thermal hyperalgesia and mechanical hypersensitivity in males treated with CFA, but only thermal hyperalgesia in CFA females. Most of the anti-hyperalgesic effects of chronic THC vapor were still observable 24 hours after cessation of the last THC exposure. We also report that chronic THC vapor inhalation modulates intrinsic and synaptic properties of vlPAG neurons, including reductions in action potential firing rate and spontaneous inhibitory synaptic transmission in males, and that these effects occur specifically in neurons that respond to current input with a "delayed" firing phenotype. Treatment with CFA led to increased firing rate and increased sIPSC amplitude in vlPAG neurons of female rats, and chronic THC vapor rescued sIPSC amplitudes to control levels - these effects were specific to vlPAG neurons categorized as having an "onset" firing phenotype. Ongoing work is exploring sex-specific mechanisms (e.g., CB1 receptor) of THC vapor rescue effects in the vlPAG of rats treated with CFA, and further exploring the vlPAG cell types impacted by CFA treatment and chronic THC vapor inhalation. Significance StatementMany adults in the U.S. with pain self-medicate with THC and cannabis, and many humans use e-cigarette type devices filled with cannabis extracts to self-administer THC and other constituents of the marijuana plant. Until recently, most rodent studies of THC effects on brain and behavior have used injection procedures and male rats. Here, we tested the effect of chronic THC vapor inhalation on pain-related behaviors and midbrain neural circuit function in adult male and female Wistar rats. As predicted, chronic THC vapor inhalation rescued chronic inflammatory pain effects on behavior and midbrain neuronal function.

neuroscience↗

bioRxiv2021

Cellular, physiological, and behavioral validation of a CRFR1:Cre-tdTomato transgenic rat for use in basic neuroscience research

Corticotropin-releasing factor type-1 (CRF1) receptors are critical to stress responses because they allow neurons to respond to CRF released in response to stress. Our understanding of the precise role of CRF1-expressing neuronal populations in CRF-mediated behaviors has been largely limited to mouse experiments due to the lack of genetic tools available to selectively visualize and manipulate CRF1+ cells in rats. Here, we describe the generation and validation of a transgenic CRF1:Cre-tdTomato rat, which expresses a bicistronic iCre-2A-tdTomato transgene directed by 200kb of promoter and enhacer sequence surrounding the Crhr1 cDNA present within a BAC clone, that has been transgenically inserted into the rat genome. We report that Crhr1 and Cre mRNA expression are highly colocalized in CRF1:Cre-tdTomato rats within both the central amygdala (CeA), composed of mostly GABAergic neurons, and in the basolateral amygdala (BLA), composed of mostly glutamatergic neurons. In the CeA, membrane properties, inhibitory synaptic transmission, and responses to CRF bath application in tdTomato+ neurons are similar to those previously reported in GFP+ cells in CRFR1-GFP mice. We show that stimulatory DREADD receptors can be selectively targeted to CeA CRF1+ cells via virally delivered Cre-dependent transgenes, that transfected Cre/tdTomato+ cells are activated by clozapine-n-oxide in vitro and in vivo, and that activation of these cells in vivo increases anxiety-like behavior and nocifensive responses. Given the accuracy of expression in the CRF1:Cre rat, modern genetic techniques used to investigate the anatomy, physiology, and behavioral function of CRF1+ neurons and circuits can now be performed in assays that require the use of rats as the model organism. Impact StatementA novel transgenic rat for studying the role of specific corticotropin-releasing factor type-1 receptor-expressing cell populations in physiology and behavior.

neuroscience↗

bioRxiv2020

Alcohol dependence activates ventral tegmental area projections to central amygdala in male mice and rats

The neural adaptations that occur during the transition to alcohol dependence are not entirely understood, but may include a gradual recruitment of brain stress circuitry by mesolimbic reward circuitry that is activated during early stages of alcohol use. Here, we focused on dopaminergic and non-dopaminergic projections from the ventral tegmental area (VTA), important for mediating acute alcohol reinforcement, to the central nucleus of the amygdala (CeA), important for alcohol dependence-related negative affect and escalated alcohol drinking. The VTA projects directly to the CeA, but the functional relevance of this circuit is not fully established. Therefore, we combined retrograde and anterograde tracing, anatomical, and electrophysiological experiments in mice and rats to demonstrate that the CeA receives input from both dopaminergic and non-dopaminergic projection neurons primarily from the lateral VTA. We then used slice electrophysiology and fos immunohistochemistry to test the effects of alcohol dependence on activity and activation profiles of CeA-projecting neurons in the VTA. Our data indicate that alcohol dependence activates midbrain projections to the central amygdala, suggesting that VTA projections may trigger plasticity in the CeA during the transition to alcohol dependence and that this circuit may be involved in mediating behavioral dysregulation associated with alcohol dependence.

neuroscience↗

bioRxiv2019

Sex differences in traumatic stress reactivity of rats with a history of alcohol drinking

BackgroundAlcohol misuse and post-traumatic stress disorder (PTSD) are highly comorbid and treatment outcomes are worse in individuals with both conditions. Although more men report experiencing traumatic events than women, the lifetime prevalence of PTSD is twice as high in females. Despite these data trends in humans, preclinical studies of traumatic stress reactivity have been performed almost exclusively in male animals. MethodsThis study was designed to examine sex differences in traumatic stress reactivity in alcohol-naive rats and rats given intermittent access to 20% ethanol in a 2-bottle choice paradigm for 5 weeks. Rats were exposed to predator odor (bobcat urine) and tested for avoidance of the odor-paired context 24 hours later; unstressed Controls were never exposed to odor. Two days after stress, we measured physiological arousal using the acoustic startle response (ASR) test. We also measured anxiety-like behavior using the elevated plus-maze (EPM) and circulating corticosterone levels before and immediately after odor exposure. ResultsMale and female rats exposed to predator odor displayed blunted weight gain 24 hours post-stress, but only a subset of stressed animals exhibited avoidance behavior. Chronic intermittent alcohol drinking increased the proportion of Avoiders in males and predator odor exposure increased ASR in these animals. Predator odor stress reduced ASR in females relative to unstressed females and stressed males, regardless of alcohol drinking history. Bobcat urine exposure did not promote persistent anxiety-like behavior, but alcohol-experienced males exhibited reduced activity in the EPM in comparison to alcohol-experienced females. Furthermore, predator odor increased circulating corticosterone levels in females relative to males and baseline. ConclusionsWe report robust sex differences in behavioral and endocrine responses to bobcat urine exposure in adult Wistar rats. Also, chronic moderate alcohol drinking increased traumatic stress reactivity in males but not females. Our findings emphasize the importance of considering sex as a biological variable in the investigation of traumatic stress effects on physiology and behavior.

animal behavior and cognition↗

bioRxiv2019

THE ROLE OF CENTRAL AMYGDALA CORTICOTROPIN-RELEASING FACTOR IN PREDATOR ODOR STRESS-INDUCED AVOIDANCE BEHAVIOR AND ESCALATED ALCOHOL DRINKING IN RATS

Post-traumatic stress disorder (PTSD) is characterized by avoidance of trauma-associated stimuli and amygdala hyperreactivity, and is highly co-morbid with alcohol use disorder (AUD). Our lab uses a predator odor (bobcat urine) stress model that produces conditioned avoidance of an odor-paired context in a subset of rats, mirroring avoidance symptoms that manifest in some but not all humans exposed to trauma. We previously showed that after predator odor stress, Avoiders exhibit escalated alcohol drinking, higher aversion-resistant operant alcohol responding, hyperalgesia, and greater anxiety-like behavior compared to unstressed Controls. We also showed that systemic antagonism of corticotropin-releasing factor-1 receptors (CRFR1) reduced escalation of alcohol drinking in rats not indexed for avoidance, that corticotropin-releasing factor (CRF) infusions into the central amygdala (CeA) produced conditioned place avoidance in stress-naive rats, and that intra-CeA infusion of a CRFR1 antagonist reduced hyperalgesia in Avoiders. Here, we show that avoidance behavior is persistent after repeated predator odor exposure and is resistant to extinction. In addition, Avoiders showed lower weight gain than Controls after predator odor re-exposure. In the brain, higher avoidance was correlated with higher number of c-Fos+ cells and CRF immunoreactivity in the CeA. Finally, we show that intra-CeA CRFR1 antagonism reversed post-stress escalation of alcohol drinking and reduced avoidance behavior in Avoiders. Collectively, these findings suggest that elucidation of the mechanisms by which CRFR1-gated CeA circuits regulate avoidance behavior and alcohol drinking may lead to better understanding of the neural mechanisms underlying co-morbid PTSD and AUD.

neuroscience↗

bioRxiv2019

Nicotine e-cigarette vapor inhalation effects on nicotine & cotinine plasma levels and somatic withdrawal signs in adult male Wistar rats

RationaleNon-contingent chronic nicotine exposure procedures have evolved rapidly in recent years, culminating in Electronic Nicotine Delivery Systems (ENDS or e-cigarettes) to deliver vaporized drugs to rodents in standard housing chambers.\n\nObjectivesThe aim of the current work was to use ENDS to test concentration-dependent effects of nicotine e-cigarette vapor inhalation on blood-nicotine concentrations, blood-cotinine concentrations, and somatic withdrawal signs over time in rats.\n\nMethodsMale Wistar rats were exposed to vapor containing various concentrations of nicotine (20, 40, 80 mg/mL) for 11 days through ENDS, and blood concentrations of nicotine and cotinine, the major proximate metabolite of nicotine, as well as spontaneous and precipitated somatic withdrawal signs were measured over time (across days of exposure and over hours after termination of vapor exposure).\n\nResultsExposing male Wistar rats to non-contingent nicotine vapor inhalation through ENDS produces somatic withdrawal symptoms and measurable blood-nicotine and blood-cotinine levels that change according to 1) concentration of nicotine in vape solution, 2) number of days of nicotine vapor exposure, 3) time since termination of nicotine vapor exposure, and 4) relative to the withdrawal signs, whether withdrawal was spontaneous or precipitated (by mecamylamine).\n\nConclusionsThe data presented here provide parameters that can be used as a reasonable starting point for future work that employs ENDS to deliver non-contingent nicotine vapor in rats, although many parameters can and should be altered to match the specific goals of future work.

neuroscience↗