An optogenetic investigation of CNS sensitization following alcohol withdrawal

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DESCRIPTION (provided by applicant): The primary objective of this project is to characterize the T-type calcium channel (T-channel) mediated neuron and circuit sensitization that occurs in the setting of alcohol withdrawal (WD) and to determine the potential utility of specific T-channel blockers as therapy in WD. WD symptoms, including seizure, represent a major barrier to recovery for alcoholics, driving many to relapse. WD symptoms become more severe with subsequent WDs; likely due to rebound hyperexcitability following chronic CNS depression through GABA modulation by alcohol. Our lab has identified the T-channel isoform Cav3.2 as a potential mediator of WD hyperexcitability, and our findings suggest that T-channels may underlie the generation and propagation of WD seizures. I propose to investigate the T-channel mediated sensitization effects of WD by testing population sensitivity using a precise optogenetic stimulation paradigm in the presence or absence of T-channel blockers. Additionally, I will use an optogenetic seizure induction method to test the efficacy of the T-channel specific anti-epileptic drug ethosuximide against the standard WD seizure prophylaxis, lorazepam. Finally, I will identify the specific sites of sensitization in a proposed WD seizure network and test the effect of T-channel blockade on the responsiveness of the network. All of the following specific aims will employ chronic multi-site electrophysiology recording paired with optical stimulation of CA1 of the transgenic Thy1-ChR2 mouse. Specific Aim 1 will evaluate sensitization of thalamic and hippocampal neuron populations following WD by quantifying interictal spikes in kindled animals before and after WD. Specific Aim 2 proposes to use an optogenetic seizure induction paradigm following WD to determine the extent to which seizure spread, intensity, and threshold are modified by WD. While Specific Aim 3 will characterize network changes following WD by recording optogenetically evoked activity at multiple sites downstream of stimulation at a range of stimulation levels. T-channel blockers will be used in all experiments to distinguish T-channel mediated effects from those related to other mechanisms. This training plan proposes a multidisciplinary approach that includes optogenetics, electrophysiology, behavioral studies, and pharmacologic intervention to identify the T-channel mediated effects on neuron sensitivity following WD as well as to identify potential novel therapies for WD seizure. The approach to this study will provide training in optogenetic techniques, electrophysiology recording and analysis, behavioral studies, and histology and microscopy. With guidance and support from my advisor and research associates; this project will provide training for the pursuit of basic and translational research questions and generate insight into the burdens of alcoholism. Finally, a clinical training plan that encompasses the duration of my basic research training will ensure that I will be well-rounded in my career as a physician-scientist.