Effects of in vivo ethanol administration on Ca2+/Mg2+ ATPase and ATP-dependent Ca2+ uptake activity in synaptosomal membranes.

Acute administration of ethanol (4 g/kg, i.p.) to mice inhibits the sequestration of calcium into endoplasmic reticulum-like organelles in synaptosomal membranes. Ethanol administration inhibits both Ca2+-stimulated adenosine triphosphate hydrolysis and ATP-dependent calcium uptake in the vesicles at time of loss of righting reflex. At recovery of righting reflex, the Ca2+-ATPase activity returns to normal levels, while the ATP-dependent uptake remains inhibited. The effect of ethanol is specific for the sequestration (active transport) of calcium since calcium binding to synaptic membranes is not altered. Alteration in mechanisms responsible for synaptosomal buffering of cytosolic Ca2+ levels by in vivo ethanol may contribute to altered transmitter release rates following ethanol administration.