Effects of tetrabenazine and of chlorpromazine on submitochondrial adenosine triphosphatases of rat brain in the presence of the soluble fraction

The effects of tetrabenazine and of chlorpromazine on Na⁺-K⁺-ATPase and Mg²⁺-ATPase in two submitochondrial fractions prepared from rat brain were studied. The soluble fraction inhibits the ATPases in the two particulate fractions. Tetrabenazine, like the catecholamines, counteracts the inhibition by the soluble fraction. Chlorpromazine inhibits differently the ATPases in the two fractions. In the presence of the soluble fraction chlorpromazine can reduce both the inhibition by the soluble fraction and the stimulation by dopamine or tetrabenazine. It is suggested that an endogenous inhibitor and the catecholamines regulate the ATPase activity of certain membrane structures of the rat brain. Drugs like tetrabenazine and chlorpromazine might affect this regulation.