Mg2+- ATPase in the fish brain and its ultrastructural localization

Effects of γ-aminobutyric acid (GABA) and ethanol on Mg²⁺-ATPase from mitochondrial and microsomal fractions of the fish brain were studied. GABA (10^-8–10^-4 M) activates microsomal Mg²⁺-ATPase, but has no effect on the mitochondrial enzyme activity. This effect of GABA on the microsomal Mg²⁺-ATPase was absent in the presence of 8% ethanol. Ethanol at 1– 10% concentrations inhibits the basal microsomal Mg²⁺-ATPase and has no effect on the mitochondria enzyme. Using cytochemical technique, Mg²⁺-ATPase was revealed both in neurons and in glial cells. The ethanol-sensitive Mg²⁺-ATPase is located in the area of synaptic junctions and is bound to plasma, vesicular, and smooth endoplasmic reticulum membranes.