Biology subjects

Hope, B. T.

Publications and source records attributed to Hope, B. T..

10 recordsLinked to original sources

bioRxiv2026

Neuronal Grin2c expression and the cocaine engram: a medial prefrontal cortex substrate for conditioned place preference

Learned associations between drugs of abuse and drug-associated stimuli are thought to be encoded by physical alterations, termed engrams, within activity-dependent neuronal ensembles. However, the molecular mechanisms that support drug-memory engrams remain largely unknown. The goal of our study was to assess transcriptional alterations as candidate engrams within medial prefrontal cortex (mPFC) ensembles selectively activated by exposure to a cocaine-paired context following cocaine conditioned place preference (CPP). Using the immediate early gene Fos to identify strongly activated neurons, we found that mPFC was strongly activated by exposure to the cocaine-paired context, but not to the unpaired saline control context. We then used a combination of fluorescence activated cell sorting (FACS) and subsequent qPCR to identify gene targets upregulated in the Fos-positive mPFC ensemble neurons relative to the Fos-negative mPFC neurons following context re-exposure. Of the genes examined, the most strongly induced in the Fos-expressing neurons was Grin2c, which encodes the NR2C subunit of the NMDA receptor. We confirmed this finding using RNAscope in situ hybridization. To assess a causal role for Grin2c in cocaine-induced CPP, we used AAV-mediated, neuron-selective expression of Grin2c microRNA to knockdown Grin2c expression in mPFC neurons, which reduced cocaine CPP and facilitated CPP extinction over repeated tests. Our results indicate that neuronal Grin2c expression in the mPFC plays a role in associative learning underlying cocaine CPP. Future studies are needed to determine whether Grin2c expression plays a broader role within engrams underlying other forms of learning and memory.

neuroscience↗

bioRxiv2026

Unique mushroom spine morphology signature in cocaine relapse ensembles in rat nucleus accumbens core

Fos-expressing neuronal ensembles in nucleus accumbens (NAc) are selectively activated by drug-associated cues and shown to play a causal role in drug-cue memories. Many unique molecular and cellular alterations have been identified in these ensembles and thought to be components of an engram encoding the memory; however, spine morphology alterations on these ensembles have rarely been examined. Here, we examined alterations of identified spine types on Fos-expressing neurons in NAc core that were selectively activated by drug-associated cues during cocaine relapse. We combined Fos immunolabeling along with viral-based sparse GFP labeling to identify Fos-positive and Fos-negative neurons with distinguishable dendrites and quantified spine composition, densities and interspine intervals (ISIs) for all spine types, and head and neck diameters of mushroom spines. ISIs and head and neck diameters of mushroom spines were altered on Fos-positive (versus Fos-negative) neurons activated during cue-induced cocaine relapse. Critically, these alterations were not found on Fos-positive neurons activated by exposure to a novel context on relapse test day, despite having identical cocaine self-administration histories. Based on previous work, this suggests these alterations were not simply due to acute activation of a randomly selected set of neurons on test day, but rather they were altered specifically on neurons selectively activated during cocaine self-administration training and then reactivated during relapse. Stubby spines and immature spines, including filopodia and thin spines, were not altered. Altogether, these mushroom spine alterations describe a unique spine morphology signature for a drug-cue memory in NAc neuronal ensembles selectively activated during cocaine relapse.

neuroscience↗

bioRxiv2026

Persistent vulnerability to heroin relapse across the adult lifespan in rats

Relapse to opioid use during abstinence is often triggered by drug-associated cues but the persistence of this effect across the lifespan is unknown. Using a rat model, we found that relapse provoked by heroin-predictive discriminative stimuli persisted for over one year of abstinence, suggesting enduring, potentially lifelong opioid relapse vulnerability.

animal behavior and cognition↗

bioRxiv2025

Distinct prelimbic cortex ensembles encode response execution and inhibition

Learning when to initiate or withhold actions is essential for survival and requires integration of past experiences with new information to adapt to changing environments. While stable prelimbic cortex (PL) ensembles have been identified during reward learning, it remains unclear how they adapt when contingencies shift. Does the same ensemble adjust its activity to support behavioral suppression upon reward omission, or is a distinct ensemble recruited for this new learning? We used single-cell calcium imaging to longitudinally track PL neurons in rats across operant food reward Training, Extinction and Reinstatement, trained rat-specific decoders to predict trial-wise behavior, and implemented an in-silico deletion approach to characterize ensemble contributions to behavior. We show that operant training and extinction recruit distinct PL ensembles that encode response execution and inhibition, and that both ensembles are re-engaged and maintain their roles during Reinstatement. These findings highlight ensemble-based encoding of multiple learned associations within a region, with selective ensemble recruitment supporting behavioral flexibility under changing contingencies.

neuroscience↗

bioRxiv2023

Transcriptional analysis of neuronal ensembles of alcohol memories within the nucleus accumbens

Alcohol-associated memories play an important role in relapse in alcohol use disorder. Disrupting these memories, which become labile upon retrieval, through interference with their reconsolidation process, could reduce relapse. Memories are thought to be encoded within specific patterns of sparsely distributed neurons, called neuronal ensembles. Here, we explored the role of neuronal ensembles in alcohol-memory reconsolidation and relapse and characterized their transcriptional signature. Upon retrieving alcohol-related memories, we observed increased neuronal activation in the nucleus accumbens (NAc). We established the causal role of these NAc ensembles in alcohol-memory reconsolidation using the Daun02 method with the Fos-LacZ transgenic rat, which expresses {beta}-galactosidase ({beta}-gal) under the Fos promoter, allowing the selective ablation of activated neurons. Selective inactivation of the active NAc neuronal ensemble produced a long-lasting attenuation of relapse. Through fluorescence-activated cell sorting (FACS) and RNA sequencing, we found a unique transcriptional fingerprint in activated Fos-positive neuronal ensembles in NAc following alcohol memory retrieval (vs. no retrieval controls) that was not present in the Fos-negative neurons. Our findings underscore the critical role of NAc neuronal ensembles in alcohol-associated memory reconsolidation. These neurons have a unique transcriptional profile that can provide novel targets for reducing alcohol relapse.

neuroscience↗

bioRxiv2023

MultipleXed Population Selection and Enrichment single nucleus RNA sequencing (XPoSE-seq) enables sample identity retention during transcriptional profiling of rare populations

Single nucleus RNA-sequencing is critical in deciphering tissue heterogeneity and identifying rare populations. However, current high throughput techniques are not optimized for rare target populations and require tradeoffs in design due to feasibility. We provide a novel snRNA pipeline, MulipleXed Population Selection and Enrichment snRNA-sequencing (XPoSE-seq), to enable targeted snRNA-seq experiments and in-depth transcriptomic characterization of rare target populations while retaining individual sample identity.

neuroscience↗

bioRxiv2022

Incubation of palatable food craving is associated with brain-wide neuronal activation in mice

Studies using rodent models have shown that relapse to drug or food seeking increases progressively during abstinence, a phenomenon termed incubation of craving. Mechanistic studies of incubation of craving have focused on specific neurobiological targets within pre- selected brain areas. Recent methodological advances in whole-brain immunohistochemistry, clearing, and imaging now enable unbiased brain-wide cellular resolution mapping of regions and circuits engaged during learned behaviors. However, these whole brain imaging approaches were developed for mouse brains while incubation of drug craving has primarily been studied in rats and incubation of food craving has not been demonstrated in mice. Here, we established a mouse model of incubation of palatable food craving and examined food reward seeking after 1, 15, and 60 abstinence days. We then used the neuronal activity marker Fos with intact brain mapping procedures to identify corresponding patterns of brain-wide activation. Relapse to food seeking was significantly higher after 60 abstinence days than after 1 or 15 days. Using unbiased ClearMap analysis, we identified increased activation of multiple brain regions, particularly corticostriatal structures, following 60, but not 15 abstinence days. We used orthogonal SMART2 analysis to confirm these findings within corticostriatal and thalamocortical subvolumes and applied expert-guided registration to investigate subdivision and layer-specific activation patterns. Overall, we (1) identified novel brain-wide activity patterns during incubation of food seeking using complementary analytical approaches, and (2) provide a single-cell resolution whole-brain atlas that can be used to identify functional networks and global architecture underlying incubation of food craving. Significance StatementRelapse to reward seeking progressively increases during abstinence, a phenomenon termed incubation of craving. Mechanistic studies of incubation can lead to novel relapse treatments. However, previous studies have primarily used rat models and targeted region-by-region analyses and a brain-wide functional atlas of incubation of reward seeking is lacking. We established a behavioral procedure for incubation of palatable food seeking in mice and applied whole-brain activity mapping with Fos as a neuronal activity marker to identify the functional connectome of this incubation. Like rats, mice showed incubation of food seeking during abstinence. Using two complementary activity mapping approaches, we identified a brain-wide pattern of increased neural activation that mirrored incubation of food seeking after 60, but not 15, days of abstinence.

neuroscience↗

bioRxiv2022

A critical contribution of a sparse neuronal ensemble in the amygdala central nucleus to extinction

Adaptive behaviour critically depends on the delicate and dynamic balance between acquisition and extinction memories. Disruption of this balance, particularly when the extinction memory loses control over behaviour, is the root of treatment failure of maladaptive behaviours such as substance abuse or anxiety disorders. Understanding this balance requires a better understanding of the underlying neurobiology and its contribution to behavioural regulation. Here, we used Daun02 in Fos-lacZ transgenic rats to delete extinction-recruited neuronal ensembles in BLA and CN and examine their contribution to behaviour in an appetitive Pavlovian task. Deletion of extinction-activated ensembles in CN but not BLA impaired the retrieval of extinction and increased activity in the BLA. The disruptive effect of deleting these CN ensembles was enduring as it hindered further extinction learning, and promoted greater levels of behavioural restoration across opposing levels of the response scale seen in spontaneous recovery and reinstatement. Our data indicate that the initial extinction-recruited CN ensemble is critical to the acquisition-extinction balance, and that greater behavioural restoration does not mean weaker extinction contribution. These findings provide a novel avenue for thinking about the neural mechanisms of extinction and in developing treatments for cue-triggered appetitive behaviours.

neuroscience↗

bioRxiv2021

Role of ventral subiculum neuronal ensembles in incubation of oxycodone craving after electric barrier-induced voluntary abstinence

We recently developed a rat model of incubation of oxycodone craving where opioid seeking progressively increases after voluntary suppression of drug self-administration by adverse consequences of drug seeking. Here, we studied the role of ventral subiculum (vSub) neuronal ensembles in this incubation, using the activity marker Fos, muscimol-baclofen (GABAergic agonists) inactivation, and Daun02 chemogenetic inactivation. We trained Sprague-Dawley or Fos-lacZ transgenic male and female rats to self-administer oxycodone (0.1 mg/kg/infusion, 6-h/d) for 14 days. The rats were then exposed for 14 days to an electric barrier of increasing intensity (0.1 to 0.4 mA) near the drug-paired lever that caused voluntary abstinence or were exposed to 14 days of forced abstinence. We tested Sprague-Dawley rats for relapse to oxycodone seeking without shock and drug on abstinence day 15 and extracted their brains for Fos-immunohistochemistry, or tested them after vSub vehicle or muscimol-baclofen injections on abstinence days 1 and 15. We performed Daun02 inactivation of relapse-activated vSub Fos neurons in Fos-lacZ transgenic rats on abstinence day 15 and then tested them for relapse on abstinence day 18. Relapse after electric barrier-induced abstinence increased Fos expression in vSub. Muscimol-baclofen inactivation or Daun02 selective inactivation of vSub Fos-expressing neuronal ensembles decreased "incubated" oxycodone seeking after voluntary abstinence. Muscimol-baclofen vSub inactivation had no effect on non-incubated opioid seeking on abstinence day 1 or incubation after forced abstinence. Our results demonstrate a selective role of vSub neuronal ensembles in incubation of opioid craving after cessation of drug self-administration by adverse consequences of drug seeking. Significance statementHigh relapse rate is a cardinal feature of opioid addiction and a major impediment for successful treatment. In humans, abstinence is often self-imposed, and relapse typically involves a conflict situation between the desire to experience the drugs rewarding effects and negative consequences of drug seeking. To mimic this human condition, we recently introduced a rat model of incubation of oxycodone craving after electric barrier-induced voluntary abstinence. Here, we used the activity marker Fos, muscimol-baclofen (GABAergic agonists) inactivation, and Daun02 chemogenetic inactivation to demonstrate a selective role of vSub neuronal ensembles in incubation of oxycodone craving after electric barrier-induced voluntary abstinence, but not in incubation of opioid craving after forced abstinence or non-incubated opioid seeking during early abstinence.

neuroscience↗

bioRxiv2018

Incubation of discriminative stimulus-controlled cocaine craving: An animal model relevant to relapse prevention

In abstinent drug addicts, cues formerly associated with drug-taking experiences gain relapse-inducing potency (\"incubate\") over time. Animal models of incubation may help develop treatments to prevent relapse, but these models have ubiquitously focused on the role of conditioned stimuli (CSs) signaling drug delivery. From a translational perspective this is problematic because people encounter these stimuli only during or after relapse. For this reason, incubation in response to discriminative stimuli (DSs) that signal drug availability before relapse, not yet examined in preclinical studies, could be more relevant to relapse prevention. We trained rats to self-administer cocaine (or palatable food) under DS control, then investigated DS-controlled incubation of craving, in the absence of drug-paired CSs. DS-controlled cocaine (but not palatable food) seeking incubated over 60 days of abstinence and persisted up to 300 days. Understanding the neural mechanisms of this DS-controlled incubation holds significant promise for drug relapse treatments.

neuroscience↗