Synaptic Mechanisms of Addiction-Related Behaviors in the Nucleus Accumbens

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Early in my career as a scientist, I decided that communication was the key to all biological processes. This ideology has evolved into a keen interest in the study of synaptic transmission. In the lab of Danny G. Winder, Ph.D. I began my training in synaptic physiology publishing many papers on modulation of excitatory synaptic transmission by metabotropic glutamate receptors and their in vivo recruitment by cocaine. During my postdoctoral training, I have continued to study synaptic transmission in reward related circuitry in the lab of Robert C. Malenka, M.D., Ph.D. Dr. Malenka is a renowned synaptic physiologist and has trained many prominent figures in the synaptic physiology and addiction fields, Antonello Bonci (NIDA), Karl Deisseroth (Stanford), Dan Feldman (UC Berkeley), Pablo Castillo (Albert Einstein), John Isaac (NIH, now Lilly), Anatol Kreitzer (UCSF), Michael Crair (Yale), and Mark Thomas (Univ. Minnesota) to name a few. It is my goal to continue this tradition by obtaining an independent lab in academia studying the role of synaptic transmission in rewarding and aversive behaviors. My area of study differs from Dr. Malenka in that in addition to excitatory transmission, I am also interested in studying inhibitory and neuromodulatory transmission onto NAc interneurons as well as primary output neurons. Eventually, I plan to expand disease models and study effects of aversive states, such as acute and chronic pain, on NAc synaptic circuitry. To do this I am utilizing state of the art techniques and sophisticated yet simple approaches to address these issues in the Nucleus Accumbens (NAc). The ultimate goal of this project is to gain a better understanding of synaptic function in the NAc circuitry and to begin to address how these circuits are recruited to elicit addiction related behaviors. The NAc, as part of the mesolimbic dopamine system, integrates a complex mix of excitatory, inhibitory and modulatory inputs to optimize adaptive motivated behaviors. Dynamic alterations in synaptic transmission within this circuitry are strongly implicated in the development and expression of addictive disorders. The specific aims involve using whole-cell recordings from in vitro slices to define basic properties of NAc neurons and how these are modified by in vivo cocaine exposure. In this proposal, the effects of in vivo cocaine exposure on synaptic properties of NAc output neurons and local microcircuit interneurons (INs) will be delineated utilizing bacterial artificial chromosome (BAC) transgenic marker mice that specifically label direct and indirect pathway medium spiny neurons (MSNs), GABAergic and cholinergic INs. Also, the synaptic properties of three distinct excitatory inputs onto NAc, MSNs and INs will be characterized and the consequences of in vivo cocaine experience on these specific inputs will be determined using virally expressed channel rhodopsin (ChR2). The objectives for the mentored phase of this proposal are: (1) to examine the synaptic properties of direct and indirect MSNs following in vivo cocaine experience, and (2) to determine if specific excitatory synaptic inputs onto these MSNs are differentially altered following in vivo cocaine experience utilizing optogenetic approaches. The independent phase will address: (1) afferent specific basal and drug-induced alterations in excitatory synaptic properties of NAc INs, (2) basal and drug-induced changes in synaptic connectivity between INs and MSNs and (3) behavioral effects of light-induced (ChR2) activation of NAc INs in drug related context, all of which utilize state-of-the-art optogenetic approaches. The results of the proposed experiments will provide a fundamental knowledge of the changes in the synaptic circuitry of the NAc in a pathophysiological state and have implications on future targets for treatment of addiction related behaviors. Additionally, the careful detailed approach of this study provides the foundation for the study of other drugs of abuse and addiction models, as well as additional affirmative disorders associated with maladaptive processes in the NAc. It is my expectation that upon completion of the mentored project I will have the technical and intellectual expertise to successfully run my own independent lab at a respected institute of higher learning. I will have developed to tools to effectively communicate these findings at meetings and in publications. Additionally, it is my belief that upon completion of these projects, I will be able to successfully compete for an R01. Ultimately, this will allow me to continue to contribute to the field of addiction research both by producing quality research and mentoring young scientists.