This application requests support for a comprehensive training plan that will enable Patrick Mulholland, Ph.D. to broaden, enhance, and refine his technical skills that are necessary for a productive independent research career. Dr. Mulholland will receive multifaceted training during the mentored phase of the award from a team of collaborating mentors that includes training in cellular and molecular biology, electrophysiology, and animal models of ethanol dependence and withdrawal. The research plan that is proposed during the independent phase builds on this training and focuses more specifically on understanding neuroplastic changes associated with chronic ethanol at the molecular level. Recent evidence suggests that ethanol- associated homeostatic plasticity involves compensatory increases in synaptic NMDA receptors that contributes to aberrant hyperexcitability upon cessation of consumption and may underlie craving that leads to the high incidence of relapse in alcohol dependent individuals. Small-conductance calcium-activated potassium (SK) channels regulate NMDA receptor-dependent calcium influx and are critical modulators of hippocampal-dependent synaptic plasticity. This is consistent with the suggestion that SK2 channels and NMDA receptors form a regulatory calcium-mediated feedback loop within individual dendritic spines. Preliminary evidence demonstrates a reduction in surface SK2 channels following chronic ethanol treatment. Thus, the overarching hypothesis is that chronic ethanol exposure leads to a homeostatic functional uncoupling of the SK2 channel-NMDA receptor feedback loop. These studies will test the hypotheses that: 1) chronic ethanol exposure produces a homeostatic reduction in SK2 channel expression and function, specifically within dendritic spines, 2) the subcellular change in SK2 channel trafficking following chronic ethanol is mediated by PKA signaling, and 3) modulation of SK channels will prevent multiple withdrawal-induced kindling in an animal model of ethanol dependence. Decreases in SK2 channels and increases in NMDA receptors may represent a common homeostatic adaptive response to prolonged reductions in NMDA receptor activity during ethanol exposure. Furthermore, this functional uncoupling of the SK2 channel-NMDA receptor calcium-mediated feedback loop may contribute to tolerance development and to withdrawal hyperexcitability. In addition, results from these studies will serve to guide Dr. Mulholland's future independent research in the area of ethanol-associated homeostatic plasticity.
Findings from these studies will provide insight into the mechanisms underlying ethanol-associated changes in the central nervous system and may identify a novel therapeutic target to reduce craving for alcohol and prevent the high incidence of relapse.
