Paul W. Czoty - US grants

Cocaine abuse has been a persistent problem for over a decade. Despite efforts to understand the basis of cocaine's addictive properties, no pharmacotherapies have proven efficacious for human use. Inhibition of dopamine uptake in key brain reward circuits has been strongly linked to cocaines' behavioral-stimulant and reinforcing effects. Pharmacological manipulations of brain serotonin activity can modulate cocaine's profile of behavioral effects. The proposed studies seek to characterize the effects of selective serotonergic agents on the behavioral and reinforcing effects of cocaine and the selective dopamine uptake inhibitor, GBR 12909, in squirrel monkeys. Furthermore, microdialysis studies in awake, behaving squirrel monkeys will provide a unique approach to understanding the relationship between the behavioral consequences of cocaine self-administration and concurrent changes on brain neurochemistry that underlie cocaine's behavioral effects. Insights gained into the interactions between brain serotonin and dopamine systems will aid the understanding of cocaine abuse as well as numerous other conditions such as schizophrenia and depression which are believed to involve functional defects in these systems.

[unreadable] DESCRIPTION (provided by applicant): Although the subjective effects of cocaine are understood to play an important role in cocaine abuse, studies in humans have revealed an incomplete overlap between discriminative stimulus (SD) and reinforcing (SR) effects of drugs. Moreover, the lack of a clear understanding of the precise roles of dopamine (DA), serotonin (5-HT) and norepinepherine (NE) in these effects has hindered efforts to develop medications for cocaine dependence. The overarching goals of the research in this proposal are to gain a better understanding of the relationship between the SD and SR effects of cocaine and to better elucidate the pharmacological and neurochemical mechanisms that underlie these effects. To accomplish these aims, rhesus monkeys will be trained to discriminate a response-contingent injection of 0.1 mg/kg cocaine from saline, with an opportunity to self-administer 0.1 mg/kg cocaine under a second-order schedule immediately following the discrimination component. Using this procedure, the effects of a range of doses of cocaine, other indirect and direct DA receptor agonists will be characterized, including direct agonists that differ in efficacy at stimulating D1- and D2-like DA receptors (Specific Aim 1). To characterize the extent of overlap of the neurochemical mechanisms involved in production of these abuse-related effects of cocaine, parallel microdialysis studies will measure extracellular DA in the ventral striatum during discrimination and self- administration components of selected doses (Specific Aim 2). Mechanisms by which 5-HT and NE can modulate the behavioral effects of cocaine will be examined in subsequent behavioral and microdialysis studies (Specific Aim 3) that characterize the effects of 5-HT and NE indirect and direct agonists on the SD, SR and neurochemical effects of cocaine. By assessing behavioral and neurochemical effects within a behavioral session in the same monkeys, these innovative studies will: (1) better describe the importance of SD effects to self-administration, (2) more clearly elucidate dopaminergic mechanisms involved in production of the abuse-related effects of cocaine, and (3) provide a unique characterization of pharmacological and neurochemical mechanisms that will aid the development of effective pharmacotherapies for cocaine dependence. Relevance: The proposed studies will provide unique information about the neurobiological mechanisms through which the addictive effects of cocaine are produced. Importantly, the results will provide novel information to aid efforts to develop effective medications for cocaine addiction, and will enhance our understanding and interpretation of data collected in animal models of drug addiction. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): Although cocaine addiction persists as a major public health concern, effective medications are currently unavailable. Development of treatments for cocaine dependence will be aided by a more thorough understanding of the effects of long-term cocaine use on the brain and the impact of these changes on cognitive function. Studies using animal models with proven validity in drug abuse research will help achieve this goal. The primary aim of this 1-year grant proposal is to implement the brain imaging techniques diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS) in monkeys to generate data to support more extensive future proposals. Additional aims are to document the effects of chronic cocaine self- administration on the brain and behavior in monkeys. To accomplish these aims, a DTI/MRS scan will be performed twice on eight female cynomolgus monkeys to establish appropriate test-retest validity (Specific Aim 1). Subsequently, monkeys will self-administer cocaine (6.0 mg/kg/day) for three months, at which time a follow-up DTI/MRS scan will be conducted. After this point, four monkeys will continue to self-administer cocaine while cocaine exposure is discontinued in the remaining four, and a final DTI/MRS scan will be conducted three months later (Specific Aim 2). In addition, cognitive function will be assessed every other week using a delayed match-to-sample task (Specific Aim 3). The overarching hypothesis is that progressive and parallel alterations will be observed in white matter integrity, neurometabolite concentrations and cognitive function during cocaine self-administration and abstinence that implicate specific brain regions and pathophysiological mechanisms in the cognitive decline observed after long-term cocaine use. Thus, in addition to providing data to support the establishment of the P.I.'s independent research career, results of the present studies will considerably enhance our understanding of the effects of chronic cocaine use, interpretation of imaging studies in human cocaine abusers, medications development, and, ultimately, treatment of cocaine dependence.

Project Summary Cocaine abuse remains a significant public health problem for which there are no widely useful pharmacotherapies. Many preclinical leads have been generated that have not translated into successful medications for cocaine dependence. One reason for this failure may be that, although up to 90% of cocaine abusers also abuse alcohol, the medications development process (both preclinical animal experiments and early clinical testing of putative medications) has taken place in subjects with no exposure to alcohol. What little data that exists regarding cocaine/ethanol interactions suggests that this may represent a significant confound; ethanol can enhance some effects of cocaine in animals and humans and attenuate others. Moreover, recent clinical trials have shown that a history of alcohol dependence can reduce the ability of medications to decrease cocaine use. The proposed studies are designed to determine how long-term ethanol drinking alters the abuse-related effects of cocaine and vice versa in nonhuman primate models. First, we will determine whether prior ethanol exposure alters acquisition and maintenance (6 months) of cocaine self- administration. Parallel brain imaging studies using positron emission tomography (PET) will characterize how self-administration of ethanol, cocaine or the combination changes the availability of brain D2-like and D3 dopamine receptors, which have been implicated in both cocaine and ethanol abuse and have been suggested as targets for pharmacotherapy development. We will then examine whether these brain imaging measures correlate with the ability of potential pharmacotherapies to decrease cocaine use. Significant relationships would indicate that such measures could be used by physicians as biomarkers for behavioral phenotypes and for treatment effectiveness. Finally, the effects of self-administered cocaine on subsequent ethanol self- administration will be determined. Taken together, these studies will provide novel translatable data describing the effects of ethanol and cocaine on each other's abuse-related effects and, by characterizing precisely how combined use of these drugs alters DA receptors, will provide novel information to help guide treatment decisions for the large majority of cocaine users who concurrently abuse alcohol.

PROJECT SUMMARY Alcohol use disorder (AUD) persists as a costly public health problem that lacks widely effective medications and strategies for prevention. The overarching scientific premise of this Project, like the others of the Wake Forest Translational Alcohol Research Center (WF-TARC), is that the neural substrates that contribute to vulnerability and resilience to AUD are not fully understood. Studies using nonhuman primate (NHP) subjects have specific advantages that make them a critical part of a comprehensive, translational approach to addressing this topic, including the possibility of experimental control not possible in human subjects and a greater similarity to humans' neurobiology compared to rodents. Group-housed monkeys form linear social hierarchies; social rank has been shown to influence sensitivity to abuse drugs, with subordinates showing vulnerability to the abuse-related effects of stimulants and ethanol (EtOH). Project 2 of the WF-TARC will exploit this differential sensitivity across social ranks to determine the behavioral and brain mechanisms that underlie vulnerability to develop AUD. Behavioral studies will characterize rank-related differences in induction of EtOH drinking, EtOH consumption over one year of 22 hours-per-day access and EtOH seeking behavior during abstinence using an extremely well-characterized NHP EtOH self-administration model of long-term drinking in humans. We will also determine whether dominant and subordinate monkeys differ in sensitivity to chronic treatment potential medications for AUD. In parallel to these experiments, brain imaging studies using magnetic resonance imaging will characterize the structural and functional differences between dominants and subordinates, and determine the specific changes that occur in grey and white matter integrity, cerebral blood flow and functional connectivity during long-term EtOH drinking and subsequent abstinence. Importantly, these NHP studies occupy a critical position in the translational structure of the WF-TARC, supporting forward and backwards translation to inform and extend findings in rodent and human projects. NHP imaging studies will focus on the same brain regions and nodes that will be imaged in human subjects and studied and manipulated in rodents. Secondary analyses on imaging data will expand this focus to the entire brain. Taken together, the results of the studies in this Project, particularly in combination with data generated in other components of the WF-TARC, will provide a comprehensive account of brain differences between populations that are resistant versus vulnerable to AUD. This knowledge will ultimately help practitioners direct preventive efforts to groups who will most benefit from them, and will identify new targets for more effective medications targeted to the most vulnerable populations.

PROJECT SUMMARY. Alcohol use disorder (AUD) persists as a costly public health problem that lacks widely effective medications. The scientific premise of the proposed research is that brain receptors for the nociceptin/orphanin FQ peptide (NOP) are promising targets for new medications, but translational studies in sophisticated nonhuman primate (NHP) models are needed to inform and direct drug development and clinical testing. This premise is based on encouraging data from rodent models and positive preliminary data from our NHP laboratory using buprenorphine and its derivative BU08028, termed a ?bifunctional? MOP/NOP agonist because it stimulates both NOP and mu opioid peptide (MOP) receptors. The proposed studies combine a well-characterized, clinically relevant NHP model of chronic ethanol (EtOH) drinking, novel NOP- and MOP/NOP-acting drugs, a translational method of pharmacotherapy assessment and noninvasive brain imaging using positron emission tomography (PET imaging). After being induced to drink EtOH using established procedures, male and female rhesus monkeys will have free access to EtOH; responding to receive food pellets will also be monitored as an index of potential side effects. Specific Aim 1 will determine the effects of buprenorphine and its derivative BU08028, in combination with drugs that selectively stimulate or block MOP or NOP receptors. The results will reveal the relative contribution of MOP and NOP receptor stimulation to the ability of bifunctional agonists to decrease EtOH drinking, indicating the ideal pharmacological profile for a medication. Next (Aim 2), drugs that possess the desired profile will be selected from among a catalog of novel compounds synthesized by Co- Investigator Dr. Stephen Husbands. Candidates will be administered daily for several months and effects on moderate and heavy drinking (6 or 22 hours per day, respectively) will be determined using a translational approach developed by the P.I. We expect to identify a compound that produces prolonged suppression of EtOH drinking without altering food-maintained responding or producing adverse effects. Aim 3 consists of PET imaging studies using the novel radiotracer [11C]NOP-1A that run parallel to Aims 1 and 2. These studies will characterize (1) the influence of basal NOP receptor availability on initial sensitivity to EtOH, (2) the effects of long-term EtOH drinking on NOP receptors, (3) the effects of efficacious treatments on NOP receptor availability, (4) the extent of recovery of NOP receptor availability during abstinence from EtOH and, importantly, (5) sex differences in all these measures. Together, the results of these studies will provide novel, translational data to support the feasibility and efficacy of developing MOP/NOP and NOP-selective agonists as novel AUD pharmacotherapies using translational, clinically relevant NHP models.