| Historically, while research on the actions of ethanol at the GABAergic synapse has focused on postsynaptic mechanisms, recent data have demonstrated that ethanol also increases both evoked and spontaneous GABA release in many brain regions. However, the mechanism through which ethanol acts to enhance GABA release is unknown. The purpose of this dissertation project was to study the mechanism responsible for ethanol-enhanced GABA release at the interneuron-Purkinje cell synapse. First, the ability of ethanol to increase GABA release was characterized with whole-cell voltage clamp recordings. Ethanol increased miniature inhibitory postsynaptic current frequency and decreased the paired-pulse ratio, which suggests that ethanol increases spontaneous and evoked GABA release, respectively.;I found that calcium release from inositol-1,4,5-trisphosphate receptors (IP3Rs) and ryanodine receptors, adenylate cyclase, protein kinase A, phospholipase C and protein kinase C all play a role in the ability of ethanol to increase spontaneous GABA release, while influx of extracellular calcium into the neuron was not involved in this mechanism. Because of the questionable selectively of the IP3R antagonist, electron microscopy was used to show that IP3Rs are located in the presynaptic terminals at this synapse. Activation of cannabinoid receptors or GABAB receptors inhibited ethanol-enhanced spontaneous GABA release, but this ethanol mechanism was unaffected by tonic activation of these receptors. It was also determined that both protein kinase A and protein kinase C contribute to the generation of spontaneous GABA release and cross-talk is not occurring between these two intracellular messengers.;Overall, the large majority of the intracellular messengers investigated were involved in ethanol-enhanced GABA release. This result is not surprising considering the promiscuous nature of ethanol and the fact that these intracellular messengers can contribute to the generation of spontaneous GABA release. The ability of ethanol to increase GABA release contributes to the GABAergic profile of ethanol, and modulation of the GABAergic system contributes to alcohol intoxication. A person who is less sensitive to the intoxicating effects of alcohol is prone to developing alcoholism; therefore, understanding the molecular mechanisms contributing to alcohol intoxication will further our understanding of this disease. |
