Marek Schwendt - US grants

DESCRIPTION (provided by applicant): Cocaine dependence remains a substantial public health problem in the United States today. There is a wide and well-documented range of adverse health, psychological and social problems associated with chronic use of cocaine. However, in spite of two decades of intense research, effective pharmacotherapies for the treatment of addiction have not been identified. One of the key challenges in the successful treatment of cocaine addiction is decreasing the vulnerability of relapse to drug-taking which persists even after long periods of abstinence. Animal models have provided evidence that drug-seeking behavior arises from persistent neuroadaptations in mesolimbic dopaminergic circuitry during acquisition and cortico-striatal glutamatergic circuitry during relapse. Accordingly, the ventral striatum has been identified as a critical element of the neurocircuitry underlying drug and cue-induced reinstatement of cocaine-seeking after extinction training. However, recent evidence indicates that the habitual or compulsive quality of persistent drug-seeking in abstinent animals which do not undergo extinction training depends on the dorsal striatum (dSTR). Activity of metabotropic glutamate receptors (mGluRs) located in the ventral striatum is thought to be important for regulating cocaine-seeking behavior and cortico-striatal plasticity. Whether mGluRs in the dSTR are involved in relapse to cocaine-seeking after abstinence is not known. Our previous studies have shown that expression of the protein termed regulator of G-protein signaling 4 (RGS4) in the dSTR is regulated by acute or chronic noncontingent exposure to psychostimulants. RGS4 is a known potent negative regulator of G?i- and G?q- coupled receptors, including mGluR1/5 receptors. Cocaine self-administration followed by prolonged abstinence resulted in a decrease of RGS4 gene expression. Re-exposure to a cocaine-paired context, which resulted in robust cocaine-seeking, normalized the reduced expression of RGS4 gene expression in the dSTR. In addition, we have demonstrated that RGS4 protein in the dSTR directly associates with mGluR5-signalling assembly. Therefore, we hypothesize that changes in RGS4 levels result in altered mGluR5-mediated cellular signaling in the dSTR that contributes to increased vulnerability to relapse after abstinence. This hypothesis will be tested by addressing the following SPECIFIC AIMS: 1) To characterize changes in membrane- and mGluR5-associated RGS4 protein in the dSTR occurring with abstinence from cocaine self- administration and after relapse to cocaine-seeking. 2) To investigate the effects of RGS4 overexpression in the dSTR on relapse to cocaine-seeking after abstinence 3) To determine the effects of RGS4 overexpression on mGluR5-mediated cellular signaling in the dSTR during relapse to cocaine-seeking after abstinence. Completion of these aims will help to fill fundamental gaps in our understanding of the intracellular mechanisms underlying relapse to cocaine-seeking behavior and potentially lead to new pharmacotherapies for the treatment of addiction. PUBLIC HEALTH RELEVANCE: Cocaine addiction remains a substantial public health problem in the United States today. It is widely recognized that high risk of relapse even after long periods of abstinence represents one of the key challenges in successful treatment of cocaine addiction. This project proposal, entitled "Striatal RGS4 Interacts with mGluR5 Signaling in Relapse to Cocaine-seeking" is aimed to study neurobiological correlates of enduring vulnerability to relapse utilizing animal model with high face validity for human cocaine addiction.

ABSTRACT Methamphetamine (meth) use disorder poses unique challenges for treatment due to the prevalence of meth- induced neurocognitive deficits. These deficits contribute to persistent relapse vulnerability and complicate recovery for meth users. Here we utilize a rodent model of extended access to self-administered (SA) meth that captures many symptoms observed in meth users, such as escalation of meth intake, higher propensity to relapse, cognitive inflexibility and deficits in episodic-like memory. Thus, this model is highly suitable for investigation of neurobiology underlying persistent meth-induced deficits and for the screening of potential novel therapeutics. Using this model, we have reported that SA meth reduces cell surface (but not total) expression of metabotropic glutamate receptors (mGlu) 2/3 in the prefrontal cortex (PFC) that persist for up to 30 days of abstinence. This finding is highly relevant for meth use disorder as: a) normal function of mGlu2/3 in the PFC is necessary for optimal cognitive performance, b) increased neuronal activity and enhanced glutamate release in the PFC observed during meth-seeking could be attributed to reduced control of mGlu2/3 over glutamatergic neurotransmission, and c) systemic and intra-PFC activation of mGlu2/3 consistently reduces drug-seeking. However, these studies did not molecularly or pharmacologically separate mGlu2 from 3, and significant differences in signaling and behavioral output occur when each receptor alone is targeted. Furthermore, no pharmacological tools exists that would reverse the loss of mGlu2 (or 3) receptor function. The present proposal is significant because it will be the first to evaluate the surface expression of mGlu2 vs. 3 separately after meth SA, or otherwise. It will also be the first to consider sex-differences as a factor in such expression. This proposal?s innovation stems from the development of novel tools (interference peptides) to increase mGlu2(3) surface availability/function after their in vivo administration. Finally, we aim to develop a highly-translational intranasal route of administration of such peptides. We hypothesize that this approach will allow for selective restoration of mGlu2 and/or 3 surface expression and function in subjects with a history of chronic meth exposure. We will test this hypothesis in the following specific aims: Aim 1- Evaluate sex-differences in surface availability and function of mGlu2 and mGlu3 in the PFC, and Aim 2- Develop and optimize the in vivo delivery of interference peptides that reverse post-meth changes in mGlu2 (or 3) surface expression and function in the PFC. To achieve these ambitious aims, we propose to develop innovative tools ? receptor-specific interference peptides. Evidence- based prediction is that these peptides will normalize the surface expression/function of mGlu2(3) without the potential side-effects produced by traditional receptor ligands. In summary, the proposed experiments will evaluate the utility of cortical mGlu2(3) receptors as a target for development of novel, neurobiologically-based treatments, that can be used to improve cognitive performance and reduce the vulnerability to meth relapse.

ABSTRACT Post-traumatic stress disorder (PTSD) is a debilitating disorder that develops in a subpopulation (~20-30%) of people exposed to a traumatic event. PTSD is highly comorbid with substance use disorder (SUD), with alcohol, stimulants and opioids being the most frequently abused drugs. Despite the prevalence of PTSD+SUD comorbidity, animal models of such comorbidity are lacking and are sorely needed to screen potential treatments. Here we will utilize our novel animal model of PTSD+SUD that captures several key features of PTSD+SUD comorbidity: 1) PTSD typically arises from a single trauma, 2) not all trauma-exposed individuals develop PTSD, 3) post-trauma anxiety symptoms are long-lasting, and 4) increased drug-craving and resistance to traditional interventions that reduce relapse in SUD. This model relies on exposing rodents to an ethologically-relevant ?trauma? - predator scent stress (PSS). We have successfully combined the PSS model of PTSD with the extended access to cocaine self-administration to study PTSD+cocaine use disorder (CUD) in animals. The present application proposes to adapt this animal model to study the interaction between opioid use disorder (OUD) and PTSD. Our overall hypothesis is that, as we demonstrated for cocaine, stress-Susceptible rats will display greater oxycodone seeking, a possible indication of similar neurobiological underpinnings of both cocaine and opioid seeking in stress susceptible rats. We will assess opioid seeking using two models. Aim 1 will utilize demand curve analyses (increasing the ?cost? to obtain intravenous oxycodone infusions over days) to calculate the essential demand for oxycodone and use regression models to assess the relationship between anxiety and oxycodone demand. This work will be done in males and females, and thus, will be the first work to assess sex differences in demand for oxycodone. We have found that stress-susceptibility results in increased cue-primed reinstatement of cocaine-seeking and impaired instrumental extinction of the response made to obtain cocaine. Aim 2 will assess if the same is true for oxycodone seeking, which would imply a common circuit or circuits mediating enhanced stress susceptibility and drug-seeking and potentially lead to pharmacotherapies for individuals with both OUD and CUD. Our rationale is that rat models that more closely model comorbidities accompanying human substance use should more accurately reproduce the underlying neuroadaptations present in humans, and should thus serve as better platforms for therapeutic discovery. As such, our central, unified hypothesis is that susceptibility to stress remodels circuits involved in drug seeking in a similar manner for cocaine and opioids. Future research proposals would interrogate neurobiological substrates and circuit(s) involved in differential oxycodone seeking. For example, we have found that mGlu5 expression in the amygdala and prefrontal cortex is increased in Resilient rats relative to Susceptible rats after re-exposure to the TMT context, two regions also implicated in extinction and seeking of drugs of abuse.

ABSTRACT Post-traumatic stress disorder (PTSD) is a debilitating disorder that develops in a subpopulation (~20-30%) of people exposed to a traumatic event. PTSD is highly comorbid with substance use disorder (SUD), with alcohol, stimulants and opioids being the most frequently abused drugs. Despite the prevalence of PTSD+SUD comorbidity, animal models of such comorbidity are lacking and are sorely needed to screen potential treatments. Here we will utilize our novel animal model of PTSD+SUD that captures several key features of PTSD+SUD comorbidity: 1) PTSD typically arises from a single trauma, 2) not all trauma-exposed individuals develop PTSD, 3) post-trauma anxiety symptoms are long-lasting, and 4) increased drug-craving and resistance to traditional interventions that reduce relapse in SUD. This model relies on exposing rodents to an ethologically-relevant ?trauma? - predator scent stress (PSS). We have successfully combined the PSS model of PTSD with the extended access to cocaine self-administration to study PTSD+cocaine use disorder (CUD) in animals. The present application proposes to adapt this animal model to study the interaction between opioid use disorder (OUD) and PTSD. Our overall hypothesis is that, as we demonstrated for cocaine, stress-Susceptible rats will display greater oxycodone seeking, a possible indication of similar neurobiological underpinnings of both cocaine and opioid seeking in stress susceptible rats. We will assess opioid seeking using two models. Aim 1 will utilize demand curve analyses (increasing the ?cost? to obtain intravenous oxycodone infusions over days) to calculate the essential demand for oxycodone and use regression models to assess the relationship between anxiety and oxycodone demand. This work will be done in males and females, and thus, will be the first work to assess sex differences in demand for oxycodone. We have found that stress-susceptibility results in increased cue-primed reinstatement of cocaine-seeking and impaired instrumental extinction of the response made to obtain cocaine. Aim 2 will assess if the same is true for oxycodone seeking, which would imply a common circuit or circuits mediating enhanced stress susceptibility and drug-seeking and potentially lead to pharmacotherapies for individuals with both OUD and CUD. Our rationale is that rat models that more closely model comorbidities accompanying human substance use should more accurately reproduce the underlying neuroadaptations present in humans, and should thus serve as better platforms for therapeutic discovery. As such, our central, unified hypothesis is that susceptibility to stress remodels circuits involved in drug seeking in a similar manner for cocaine and opioids. Future research proposals would interrogate neurobiological substrates and circuit(s) involved in differential oxycodone seeking. For example, we have found that mGlu5 expression in the amygdala and prefrontal cortex is increased in Resilient rats relative to Susceptible rats after re-exposure to the TMT context, two regions also implicated in extinction and seeking of drugs of abuse.