Joshua A. Lile - US grants

The goal of this proposal is to achieve a better understanding of the pharmacological and behavioral determinant of the reinforcing effects of cocaine, a heavily abused substance in all social strata. Cocaine binds to the dopamine (DA), and to a lesser extent, the serotonin (5-HT) and norepinephrine (NE) transporters, blocking the reuptake of these monamines. Research with animals has shown that DA neurotransmission, in large part, mediates the reinforcing effects of cocaine. Less information, however, is available regarding the interactions of cocaine with the 5-HT system. The studies proposed in this project are designed to evaluate, using rhesus monkeys, the reinforcing efficacy of tropane analogs having differential selectivity and duration of action at the DA and 5-HT transporters, as well as their ability to affect cocaine self-administration using fixed-ratio and progressive-ratio schedules of reinforcement. Specifically, this proposal will 1) investigate the ability of these tropanes to maintain self-administration when substituted for cocaine; 2) determine the reinforcing efficacy of these tropanes relative to cocaine: 3) evaluate the ability of chronic treatment with these tropanes to selectively decrease cocaine self- administration; 4) investigate the effects of discontinuation of treatment on cocaine's reinforcing effects. When completed, this research will provide additional information regarding the relative importance of the DA and 5-HT systems in mediating the reinforcing effects of cocaine. In addition, it will evaluate the ability of longacting tropanes with differential selectivity for the DA and 5-HT transporters to decrease maintenance and relapse to cocaine self- administration, an animal model of cocaine abuse in humans.

DESCRIPTION (provided by applicant): Dr. Lile's graduate and post-doctoral research focused on the neuropharmacological basis of stimulant addiction and how the neurotransmitter systems that mediate the effects of stimulants could be targeted for medications development. The career development and research plan proposed in this application outlines the training that will enable him to apply his previous experience, along with new methodolgies, to an emerging area of research, the treatment of cannabis-related disorders. Despite the fact that cannabis use is more prevalent than for any other illicit drug and can progress to abuse and dependence, there are no pharmacotherapies for these disorders and little clinical research has been conducted to this end. The experiments described here were designed to identify the neurotransmitter systems that are involved in the effects of the primary active constituent of cannabis, delta 9-THC, in humans. The primary outcome variable for these experiments is the interoceptive cue produced by delta 9-THC. The interoceptive effects of delta 9- THC will be measured using the drug-discrimination procedure, which is a pharmacologically specific and sensitive means to characterize the profile of a drug. Because cannabis-related disorders are associated with maladaptive changes in behavior and cognition, additional experimental measures to assess reinforcement, subjective ratings, impulsivity, psychomotor performance, learning and memory will also be taken. The role of the cannabinoid, opioid, GABA and dopamine systems will be investigated, which will reveal targets for future research efforts. Dr. Lile will be sponsored by Dr. Kelly, an expert in cannabis research in humans. The conduct of these experiments and the training described in this proposal will occur at the University of Kentucky, which has an extensive community of scientists engaged in basic and clinical research related to drug addiction. This award will allow Dr. Lile to develop as an independent investigator and to establish a program of human research concentrated on cannabis-related disorders.

DESCRIPTION (provided by applicant): Cannabis remains the most commonly used illicit drug worldwide, including the United States. Not only does a relatively large percentage of the population report using cannabis, but like other drugs of abuse, a significant proportion of those persons use it habitually and meet diagnostic criteria for drug-use disorders. Moreover, cannabis-use disorders are associated with treatment admission and relapse rates comparable to other drugs of abuse perceived as more harmful. Despite the significant public health concern posed by cannabis use, there has been limited preclinical or clinical research that has focused explicitly on the identification and development of medications to treat cannabis-use disorders. Data from preclinical and clinical research suggest that agonist replacement treatment is an effective means to manage drug-use disorders, and that this strategy would be viable for cannabis-use disorders as well. The experiments proposed here represent the initial step of evaluating GABAergic drugs as potential "agonist-like" pharmacotherapies for cannabis-use disorders. GABA is being targeted because there is substantial overlap in the effects produced by cannabinoids and drugs acting at central GABAergic systems, and neuroanatomical, neurochemical and behavioral studies support a functional link between cannabinoid and GABAergic systems. The studies proposed here will test the ability of the selective GABA reuptake inhibitor tiagabine, the GABAA positive modulator diazepam and the GABAB agonist baclofen to enhance the behavioral and physiological effects of ?9-THC, thus examining the "agonist-like" profile of GABAergic drugs with varying mechanisms of action. The primary outcome for these experiments is the interoceptive cue produced by ?9-THC. The interoceptive effects of ?9-THC will be measured using the drug-discrimination procedure, which is a pharmacologically specific and sensitive means to characterize drugs and drug interactions. In addition, subjective effects questionnaires, psychomotor performance and memory tasks, and cardiovascular and thermal measures of physiology will be included to more fully assess the effects of ?9-THC alone and in combination with GABAergic compounds. The experiments proposed here are novel and innovative because there are very few studies in humans to have tested the effects of GABAergic drugs on cannabinoids. In addition, these studies are important for at least three reasons. First, and perhaps most importantly, the data generated from the proposed experiments will provide the direction and foundation for future studies aimed at the development of GABAergic treatments for cannabis-use disorders. Second, these data will provide valuable information regarding the neurobiology of the effects of cannabinoids in humans by examining the interactions between cannabinoid and GABAergic systems. Finally, these experiments will provide translational information regarding the extent to which the results from preclinical studies that have evaluated CB-GABA interactions generalize to humans. Public Health Relevance: Cannabis is the most commonly used illicit drug in the United States and its use is associated with rates of development of abuse and dependence, treatment admission and relapse that are comparable to other illicit drugs that are misperceived as more harmful. Currently there is no effective pharmacological treatment for cannabis-use disorders. The experiments proposed here represent the initial step of evaluating GABAergic drugs as potential pharmacotherapies by characterizing interactions between ?9-THC and the selective GABA reuptake inhibitor tiagabine, the GABAA positive modulator diazepam and the GABAB agonist baclofen.

DESCRIPTION (provided by applicant): Cannabis is the most commonly used illicit drug in the United States, and its use is associated with rates of development of abuse and dependence, treatment admission and relapse that are comparable to other illicit drugs. Currently there is no effective pharmacological treatment for cannabis-use disorders. The overarching goal of my career is to develop a clinical research program in which I am able to screen potential medications for cannabis-use disorders using an efficient, evidence-based progression of laboratory procedures followed by an evaluation of the efficacy of promising leads in dependent, treatment-seeking individuals. My graduate and post-doctoral training and K01 and R01 support have enabled me to build an independent research program in which rational targets for medications development are identified based on the neuropharmacology of 9-THC. My research has identified compounds that could represent major breakthroughs in cannabis-use treatment. The goal of this K02 award is to continue my career development trajectory by acquiring the additional skills and experience needed to move my research into the next steps of the screening process. In order to achieve this goal, I have formulated a career development plan that includes additional coursework, training with expert preceptors, relevant research and data publication/presentation activities, further grant development, and the receipt and delivery of training in the responsible conduct of research. The research to be conducted during the funding period consists of a three-step screening process to 1) identify targets and/or specific compounds for subsequent screening;2) test the safety and tolerability of cannabis administration during maintenance on candidate medications;and 3) test the ability of maintenance on putative pharmacotherapies to attenuate the reinforcing effects of cannabis under controlled laboratory conditions while simultaneously monitoring changes in cannabis use in the natural ecology. Importantly, this last step represents an innovative approach that will enhance the efficiency of early phase clinical trial research, direct the choice of candidate medications for full scale clinical efficacy testing, and facilitate my eventual transition to clinical trials research. This research will be carried out in the Department of Behavioral Science at the University of Kentucky, which is an exceptional environment, having the necessary physical and intellectual resources for successful completion of the proposed career development plan. Moreover, this institution is committed to my scientific development and has acknowledged that my research program is an integral part of its scientific community. I have a solid foundation of training and research experience, have established a strong record of productivity and independent funding, and have demonstrated a commitment to mentoring the next generation of scholars interested in the treatment of cannabis-use disorders. The career development activities supported by the K02 award will allow me to sustain and expand these efforts, and thus meet my career goals, which will directly impact the field of cannabis-use treatment. PUBLIC HEALTH RELEVANCE: Cannabis is the most commonly used illicit drug in the United States, and its use is associated with rates of development of abuse and dependence, treatment admission and relapse that are comparable to other illicit drugs. Currently there is no effective pharmacological treatment for cannabis-use disorders. Five years of funding is requested to support full-time (100% effort) research and training to support the development of an efficient evidence-based medication screening process.

DESCRIPTION (provided by applicant): Cocaine-use disorders continue to be a significant public health concern, yet no effective pharmacological treatments have been identified. This application is founded on the proposition that translational research on development of cocaine pharmacotherapies will benefit from the use of coordinated and homologous procedures in animals and humans to study effects of Candidate medications on choice between cocaine and a non-drug reinforcer. Self-administration procedures will be used in this project because the reinforcing effects of drugs are central to their abuse and the development of dependence. An alternative reinforcer to cocaine will be offered because the choice to use cocaine to the exclusion of other behaviors is a hallmark of dependence, and an effective medication should assist patients in reducing drug use and reallocating behavior from drug use to more responsible and productive activities. Advantages of including preclinical research in the medications development process include strict control over environment and subject history, and testing novel compounds and/or extensive dose ranges not feasible in humans. Rhesus monkeys were selected as the animal subjects because they are phylogenetically more closely related to humans than rodents, and can be instrumented with chronically indwelling IV catheters, which facilitates implementation of drug vs. food choice procedures. Human laboratory research permits the testing of putative pharmacotherapy effects on challenges with the abused drug in a clinically relevant subject population. Another advantage of pairing rhesus monkey and human laboratory models is that powerful within-subjects designs can be used with both species. Despite the relative strengths of human and non-human primate approaches, translational research has been hampered by the use of widely different self-administration procedures and medication treatment regimens. The proposed project seeks to harmonize rhesus monkey and human procedures used to screen medications by first establishing parallel self-administration methods that will employ the same cocaine doses, route of cocaine administration and schedule of reinforcement, as well as a species-specific alternative reinforcer that effectively reduces drug taking. Cocaine doses, schedule parameters and alternative reinforcer magnitude will then be adjusted to obtain equivalent functional effects prior to d-amphetamine maintenance testing. The use of d-amphetamine will permit equilibration of cross-species sensitivity and provide a comparator for effects of other, non-dopaminergic Candidate medications examined in future studies. Achieving the aims of this project will exert a sustained and powerful impact by establishing a research platform for cocaine medication screening that will tightly link animal and human approaches thereby accelerating translational research on medications development. The proposed project is highly innovative in that it will develop coordinated and homologous procedures in nonhuman primates and humans using sophisticated cocaine choice procedures aimed towards medications development for cocaine-use disorders.

DESCRIPTION (provided by applicant): Cannabis use disorders are a significant public health concern and the absence of effective medications is a critical barrier to overcome. This application is founded on promising results from our laboratory suggesting that drugs that act at a2d-1 subunit containing voltage-dependent calcium channels (VDCCs) and/or elevate g- aminobutyric acid (i.e., GABA) will be effective medications for cannabis-use disorders. Our laboratory results are supported by a recent pilot clinical trial showing that gabapentin, which is a VDCC ligand and elevates GABA, reduced cannabis use in dependent, treatment-seeking adults. The goal of the present proposal is to build upon these promising laboratory and clinical findings by determining the ability of outpatient maintenance on pregabalin, a next generation VDCC ligand, and tiagabine, a GABA reuptake inhibitor, to attenuate the reinforcing effects of cannabis. Pregabalin will be tested because, although their mechanism of action is the same, the pharmacokinetic profile of pregabalin is improved compared to gabapentin, and clinical results suggest that this translates into greater pharmacotherapeutic effectiveness. Tiagabine will be tested because its effects overlap with gabapentin and pregabalin, GABA elevation is a possible mechanism for gabapentin's effects on cannabis use, and our recent data demonstrated that tiagabine produced a profile of effects that was comparable to gabapentin when tested in combination with D9-THC. Outpatient maintenance dosing will be tested because it more closely resembles the clinical treatment situation. Cannabis self-administration using a concurrent progressive-ratio drug-money choice procedure will be the primary outcome because drug seeking and drug taking behaviors, and the choice to use drugs to the exclusion of other behaviors, are defining characteristics of drug dependence, and drug self-administration procedures are predictive of therapeutic efficacy. Cannabis use in the natural environment will also be monitored during drug maintenance as a secondary outcome to optimize resource management and quicken the pace of intervention development. Our preliminary data with the proposed procedures support the feasibility of the project, the assembled research team is highly qualified and the environment will significantly contribute to the success of the research. The proposed project is innovative because it employs a novel hybrid procedure to study the impact of medication maintenance on direct cannabis effects in the laboratory as well as cannabis use in the natural environment, the effects of pregabalin and tiagabine on cannabis self-administration have not been tested previously, and a novel, real-time medication maintenance compliance technology will be implemented. Positive findings will exert an immediate and sustained impact by rapidly advancing currently available medications for the treatment of cannabis-use disorders, promoting novel pharmacological targets for further medications development and providing valuable basic science information about the mechanisms underlying cannabis reinforcement.

ABSTRACT Cocaine use disorder (CUD) is characterized by the decision to use cocaine at the expense of other activities. Lab-based efforts to address this problem have therefore included cocaine choice self-administration procedures that incorporate a non-drug alternative to model this defining feature. Studies using these procedures have typically scheduled competing reinforcers so that the probabilities are certain. However, such deterministic outcomes are not representative of real-world scenarios in which the consequences from drug-related decisions are often unpredictable. Importantly, decision-making in a dynamic, uncertain context significantly alters the value of choice options and requires continuous updating of option values, which engages learning processes and related corticostriatal networks that might be functioning abnormally in CUD. Decision-making in dynamic environments has been successfully modeled using probabilistic reinforcement-learning choice (PRLC) tasks. The integration of these tasks with reinforcement-learning (RL) modeling has been used to capture moment-to- moment changes in the mechanisms of dynamic choice, and the application of neuroscience techniques has begun to identify the underlying neurobiology. This approach has uncovered biologically-based decision-making abnormalities in multiple brain disorders, but has yet to be systematically applied to the experimental study of CUD, The translation of combined RL and neuroscience approaches to CUD is logical considering the maladaptive choice behavior that typifies the disorder, the varying reinforcement probabilities in cocaine users? natural environments, and the learning impairments and neuroadaptations that have been documented in individuals with CUD. Thus, there are critical gaps in our understanding of the mechanisms underlying dynamic cocaine use decisions, and a strong scientific premise for applying an RL framework to fill these gaps. This project proposes rigorous PRLC tasks, RL modeling, neuromodulation/fMRI neuroimaging techniques and complementary, translational study designs in rats and humans to study dynamic choice in CUD. The first set of cross-species experiments will demonstrate the impact of problematic cocaine use on dynamic decision-making and reveal the neurobehavioral and neurobiological processes underlying this abnormal task performance. The second set of experiments will use a PRLC task in which intravenous cocaine is available as an alternative to the non-drug reinforcer to determine the behavioral and neural ?profile? associated with the decision to use cocaine and reduced cocaine choice during treatment. Amphetamine maintenance and non-drug alternative reinforcer treatments reduce cocaine choice, which will be leveraged here to uncover behavioral and neural mechanisms that can be targeted for future treatment development. This project will have a significant impact on the field by establishing the experimental application of reinforcement-learning theory to the study of maladaptive dynamic decision-making in CUD.

ABSTRACT Opioid use disorder (OUD) is characterized by the decision to use opioids at the expense of other activities. Lab-based efforts to address this problem have therefore included opioid choice self-administration procedures that incorporate a non-drug alternative to model this defining feature. Studies using these procedures have typically scheduled competing reinforcers so that the probabilities are certain. However, such deterministic outcomes are not representative of real-world experiences in which the consequences from drug-related choices are often unpredictable. Importantly, decision-making in a dynamic, uncertain context significantly alters the value of choice options and requires continuous updating of option values, which engages learning processes and related corticostriatal networks that function abnormally in OUD. Decision-making in dynamic environments has been successfully modeled using probabilistic reinforcement-learning choice (PRLC) tasks. The integration of these tasks with reinforcement-learning (RL) computational modeling has been used to capture moment-to- moment changes in the mechanisms of dynamic choice, and the application of neuroscience techniques has begun to identify the underlying neurobiology. This approach has uncovered biologically-based decision-making abnormalities in multiple brain disorders, but has yet to be systematically applied to the experimental study of OUD, The translation of combined RL and neuroscience approaches to OUD is logical considering the maladaptive choice behavior that typifies the disorder, the varying reinforcement probabilities in opioid users? natural environments, and the learning impairments that have been documented in individuals with OUD. Thus, there are critical gaps in our understanding of the mechanisms underlying dynamic opioid use decisions, and a strong scientific premise for applying an RL framework to fill these gaps. This project proposes rigorous PRLC tasks, RL modeling, neurorecording/fMRI neuroimaging techniques and complementary, translational study designs in rats and humans. The first set of cross-species experiments will demonstrate the impact of opioid exposure and withdrawal on dynamic decision-making and reveal the neurobehavioral and neurobiological processes underlying abnormal task performance. The second set of experiments will use a PRLC task in which intravenous remifentanil, a prototypical opioid agonist with a favorable safety profile, is available as an alternative to a non-drug reinforcer to determine the behavioral and neural ?profiles? associated with drug choice, as well as the increases and decreases in drug choice that occur during withdrawal and in the presence of a large magnitude alternative reinforcer, respectively. This project will have a significant impact on the field by establishing the experimental application of reinforcement-learning theory to the study of maladaptive dynamic drug-use decision-making in OUD to reveal behavioral and neural mechanisms that can be targeted for future prevention and treatment development.