The proposed research intends to elucidate the mechanisms by which ethanol (EtOH) modulates large conductance Ca2+-activated K+ (BK) channels. Our laboratory has shown that EtOH at clinically relevant concentrations (10- 100mM) potentiates the activity of BK channels in dissociated nerve terminals isolated from the rat neurohypophysis. A fundamental question regarding EtOH is whether the drug modulates ion channels by directly binding to a hydrophobic pocket on the protein or indirectly by perturbing the surrounding lipids. Attempts to address this issue are clearly complicated by the necessity of membrane lipid for channel function. Study of EtOH's actions in extremely simplified systems would likely bring insight to this issue. We propose to determine whether the presence of channel protein and lipid are sufficient for EtOH-s action by asking whether EtOH potentiates neurohypophysial BK channels reconstituted in planar artificial bilayers. Several lines of evidence also suggest that EtOH-lipid interactions are germane. To address this issue, we will evaluate the lipid dependence of EtOH's effects.