The research proposal investigates how ethanol exposure induces brain circuit remodeling to result in persistent ethanol consumption. This project will focus on a brain region that strongly controls habits, the striatum. Habit formation i dependent upon endocannabinoid signaling through the cannabinoid type 1 receptor (CB1), a presynaptic terminal protein that mediates lasting forms of synaptic plasticity. The majority of striatal CB1 is localized to inhibitory microcircuit terminals, which potently control the functionl output of this brain region. Interestingly, several lines of evidence now indicate a direct effect f ethanol on the endocannabinoid system. Despite the relevance of striatal control of habits to alcoholism, a paucity of data exists in this regard. This proposal seeks to understand how acute and chronic ethanol exposure remodels the striatal inhibitory microcircuitry to promote habitual ethanol consumption. This will be investigated through three specific experimental aims. 1) Determine the acute effects of ethanol on GABAergic transmission at specific striatal inhibitory microcircuit synapses.
This aim will be accomplished by exposing acute mouse brain slices to ethanol and optogenetically assessing effects on the strength and plasticity of specific striatal inhibitory microcircuit synapses. The molecular mechanism underlying these changes will be examined by assessing the interaction between ethanol and the endocannabinoid system. 2) Assess the chronic effects of ethanol drinking in the dark (DID) on GABAergic transmission at synapses of the striatal inhibitory microcircuitry. The DID paradigm models long-term, binge-like ethanol consumption present in the human condition. To examine DID-induced lasting changes to striatal inhibitory microcircuit synapses of mice, brain slices will be made and the ethanol-induced changes to efficacy and plasticity of specific microcircuit synapses will be assessed. We will test how these maladaptive homeostatic responses of the inhibitory microcircuitry arise from ethanol-induced perturbation of the endocannabinoid system. 3) Determine the contribution of the striatal inhibitory microcircuitry to DID-induced increased ethanol consumption using in vivo optogenetics. To accomplish this aim, a specific cell type comprising the inhibitory microcircuitry will be reversibly inhibited on-line, with millisecond precision, durng drinking behavior in the DID paradigm using an optogenetics approach in vivo. The contribution of this manipulation during DID to post-DID ethanol consumatory behavior will be assessed using a two-bottle (ethanol and water) choice assay. The results of these studies should provide significant advances in our knowledge of how the reinforcing effects of ethanol are mediated by brain circuit-specific alterations. In my graduate and postdoctoral training, I gained the necessary training in neuroanatomical and electrophysiological techniques necessary to effectively execute this research proposal. In my graduate work under Dr. Ariel Y. Deutch, I trained extensively in neuroanatomical and behavioral pharmacology techniques including stereotaxic microinfusion of neuronal tract tracers and toxins, imaging mass spectrometry, immunohistochemistry, and behavioral measures of motor control. Through this training, I gained an expert ability to conceptualize brain circuitry. In my postdoctoral training under Dr. David M. Lovinger, I have become proficient in electrophysiological analyses assessing synaptic function. Moreover, I have pioneered the use of optogenetics in the lab, aided by my stereotaxic surgery abilities, for determining the contribution of synapse-specific changes to circuit remodeling. During the mentored phase of the proposal, research will be conducted at NIAAA in the laboratory of Dr. David M. Lovinger, my mentor. Dr. Andrew Holmes will serve as my co-mentor. Dr. Lovinger is an authority in ethanol and synaptic plasticity research and has extensive experience in in vitro and in vivo electrophysiological recording. Dr. Holmes, a behavioral neuroscience and ethanol research expert, will oversee my continued training in assessing animal behavior. With the combined collaboration of Dr. Veronica Alvarez and Dr. Geroge Kunos, both at NIAAA, all experimental tools and research guidance necessary for executing the research proposal will be readily accessible. Finally, the resources available at NIAAA for developing my teaching, mentorship, managerial, grant writing, and responsible conduct of research skills create a supportive environment in which to readily accomplish my proposed training plan.
Alcohol abuse and alcoholism impose a tremendous public health burden. Unfortunately, no effective therapy for alcoholism currently exists. This research uses mice to understand how the reinforcing properties of ethanol are mediated by remodeling of specific brain circuits that control habits. The data derived from this study should provide novel therapeutic strategies targeting alcohol dependence.
