Stimulation of cerebral cortical synaptosomal Na-K-ATPase by biogenic amines

The amines noradrenaline, dopamine, 5-hydroxytryptamine, and histamine (0.01-0.5 mM) enhanced the activity of Na-K-ATPase (EC 3.6.1.3) in rat cerebral cortical synaptosomal fractions. The activities of Mg-ATPase and Ca-Mg-ATPase were not significantly affected. No stimulation of Na-K-ATPase occurred in the presence of chelating agents (0.5 mM EGTA or EDTA) unless 0.5 mM calcium had also been added to the incubation medium. These results are consistent with the hypothesis that amines depress cerebral cortical neurones by activation of an electrogenic sodium pump. Calcium ions appear to be involved in this process.