Over 100 million Americans consider themselves to be regular drinkers, and approximately 20 percent of these individuals will eventually develop alcohol-related problems. Despite the staggering socio-economic cost of alcoholism, little is known about either the physiological factors the predispose an individual to this disease or about the molecular mechanisms that mediate the intoxicating actions of alcohol. We hypothesize that a better understanding of the molecular targets of alcohol and the physiological mechanisms that regulate ethanol sensitivity at these sites will facilitate the development of more effective treatment strategies. The overall aim of this research project is to characterize the synaptic mechanisms underlying ethanol potentiation of GABAA receptor-gated inhibitory synaptic transmission. The GABAA receptor mediates the majority of fast inhibitory synaptic transmission in the mammalian CNS, and a considerable volume of evidence suggests that these receptors may be one of the major CNS mediators of ethanol intoxication. However this interaction has not been studied, in detail, at the level of the synapse. Preliminary evidence from our laboratory indicates that ethanol may enhance GABAA receptor-mediated synaptic transmission via both a postsynaptic effect (possibly reflecting a direct interaction with GABAA receptors) and a previously uncharacterized presynaptic facilitation of GABAA receptor-mediated synaptic transmission. The first set of experiments will use the whole cell patch clamp technique to record from hippocampal CA1 pyramidal neurons in brain slices from mature rats. By characterizing the effects of ethanol (1-100 mM) on spontaneous and miniature GABAA receptor- mediated synaptic currents and currents evoked by somatic application of low concentrations of GABA, the specific mechanisms through which ethanol enhances presynaptic and postsynaptic components of GABAA receptor-gated synaptic transmission at a central mammalian synapse will be elucidated. The second series of experiments will use similar electrophysiological methods to characterize the mechanisms through which antagonism of GABAB receptors and elevation of basal PKC activity facilitate ethanol enhancement of GABAA receptor-mediated synaptic transmission. The results of these experiments will clarify the pharmacological relevance of presynaptic and postsynaptic ethanol actions to its facilitatory effect on GABAA receptor-gated synaptic transmission and identify mechanisms underlying the physiological regulation of ethanol sensitivity at these sites.
