Mark J. Ferris - US grants

DESCRIPTION (provided by applicant): The K99/R00 research and training plan will serve two purposes. The first is to provide substantial career development by: 1) expanding the investigator's area of expertise to include acetylcholine systems and their interaction with mesolimbic dopamine, 2) expanding the investigator's technical skill set to include rodent self-administration and fast scan cyclic voltammetry in freely moving animals, particularly in the detection of cue-evoked dopamine release, and 3) initiating a research program that will lead to research independence through professional development and collection of preliminary data for major research (R01) funding. The second corresponding purpose is to characterize a neurobiological mechanism for individual differences in the acquisition of drug self-administration behavior. Using a series of neurochemical and behavioral measures including microdialysis, HPLC, voltammetry in anesthetized and freely-moving animals, and self-administration, we will characterize individual differences in the magnitude of primary reward and conditioned cue-evoked dopamine release as well as corresponding propensity to self-administer cocaine and natural rewards. In addition, we will pharmacologically manipulate ventral tegmental area (VTA) and nucleus accumbens (NAc) nicotinic acetylcholine receptors (nAChRs) via acute and chronic administration of nicotine and subtype specific nAChR antagonists in order to demonstrate individual differences in their ability to modulate reward and cue-evoked dopamine transients. We propose that an underlying mechanism to explain individual differences in acquisition of drug self-administration behavior resides in the differental ability of VTA and NAc nAChRs to modulate dopamine release in the shell of the NAc in fast and slow acquiring animals. PUBLIC HEALTH RELEVANCE: Drug abuse, including cocaine addiction, is a major concern for public health and safety as it affects millions of individuals worldwide, leading to hospitalizations, incarceration, and even death. The cost to society reaches the hundreds of billions in the United States alone. The goal of this research is to understand the neurochemical mechanisms and potential risk factors that contribute to individual differences in propensity to abuse substances, particularly cocaine, so that ultimately, this information can be used to develop preventative measures to reduce drug abuse in vulnerable populations.

Center for the Neurobiology of Addiction Treatment Animal and Tissue Core Summary Dr. Mark Ferris, Core Director; Dr. Paul Czoty, co-investigator The overall objective of the Animal and Tissue Core is to generate, track and distribute tissue from experimental animals to multiple in vivo and in vitro experiments. The Core will centralize and standardize the generation, storage and transfer of brain tissue from rodents to Projects 2 and 3. These studies include self- administration, viral mediated gene knockdown of dopaminergic D2 receptors and acute/chronic treatment with putative medications identified in Project 1. By taking responsibility for the generation of these animals for studies in Projects 2 and 3, the Core will ensure that all subjects will be treated and euthanized in a standardized manner. Brain and peripheral tissue will be organized and stored by the Core, which will ensure accurate recording of the subjects' behavioral and pharmacological histories. The Core will distribute this tissue under blinded conditions to investigators in Projects 2 and 3 for imaging and biochemical studies. Careful preparation and handling of these samples and meticulous organization of information are required to ensure that reliable conclusions can be obtained from experiments using these tissue samples, which makes the Animal and Tissue Core an essential component of the Center. The specific goals are: 1. To generate groups of rats with viral mediated gene knockdown targeted against D2 receptors for Projects 2 and 3. 2. To generate groups of rats with a history of cocaine self-administration (with and without medication treatment and viral mediated gene knockdown) for Projects 2 and 3. 3. To provide a central locus for detailed record-keeping for all tissues stored within the Core and to provide timely distribution of this tissue under double-blinded conditions to Projects 2 and 3. 4. To collect and bank rodent brains that will be generated by cocaine self-administration studies in Project 1 for biochemical analyses of putative treatment drugs and other potential future uses. 5. To collect and bank nonhuman primate blood and cerebrospinal fluid (CSF) for analysis of metabolites of putative treatment drugs and other potential future uses, and bank nonhuman primate brain samples as they become available after studies in Project 1 are completed. 6. To maintain the tissue bank and periodically biopsy tissue to ensure tissue integrity.

PROJECT SUMMARY Despite decades of critical research into its biological mechanisms and treatment approaches, Substance Use Disorder (SUD) persists as a major world health problem. In the last few years, approximately 21 million people required SUD treatment. Still, recent years have seen dramatic increases in the number of overdose deaths due to heroin, prescription opioids, and cocaine. Interestingly, there is some work that suggests a circadian rhythm and robust time-of-day shifts in the function of specific receptors and neurotransmitter systems that are routinely implicated in drug abuse vulnerability and relapse. For example, diurnal (i.e., light/dark) variation has been observed in mesolimbic dopamine (DA) system, including rhythms in extracellular DA tone, DA transporter levels/ function, and DA receptor function. Moreover, research in both humans and animal models has observed that level of drug taking and seeking can vary throughout the day. While published work demonstrates regulators of diurnal variation in DA tone and tone regulators, there is a large gap in research dedicated to understanding regulators of diurnal variation and circadian rhythms in subsecond, phasic DA release. This is particularly important given the role of phasic DA release in reinforcement learning, motivation, and goal-directed behavior that is altered in SUD. Moreover, little work has been dedicated to understanding how the function of intrinsic modulators of phasic DA release, such as acetylcholine (ACh) from striatal cholinergic interneurons, vary across time-of-day. Therefore, the overall objective of this research proposal is to determine the circadian diurnal differences in rapid DA and ACh signaling and how these rhythms are mechanistically linked to changes in motivated behavior, cocaine/reward seeking, and cue-reward associations. Our central hypothesis is that there are times-of-day that individuals will exhibit increased sensitivity to reward- and cocaine-associated cues that can lead to cocaine seeking, which are mediated by time-of-day variations in the cholinergic interneuron modulation of rapid DA signaling. Specific Aim 1 will use rat models to investigate diurnal variation in 1) incentive motivational value towards reward-associated cues using pavlovian conditioned approach task, 2) the degree to which cues increase instrumental responding using a pavlovian-instrumental transfer task, and 3) the subjective value of cocaine and corresponding motivation to take cocaine. We will also examine the magnitude of both DA and ACh signaling in the nucleus accumbens (NAc) core using ex vivo fast scan cyclic voltammetry across the light / dark cycles. Specific Aims 2 and 3 will utilize voltammetry, fiber photometry, and optogenetics in freely- behaving rats to measure diurnal modulation of phasic DA and CIN activity across a 24-hour day and define a circuit specific mechanism for differences in motivated behavior, cocaine seeking, and corresponding magnitude of NAc DA signals across the light and dark cycle.