[Nature of the melipramine inhibition of the K+-n-nitrophenyl phosphatase activity of a synaptosomal fraction].

The influence of antidepressant melipramine (imipramine) on the K+-paranitrophenyl-phosphatase (K+-n-NFP-ase) activity of the synaptosomal fraction in the bull's brain cortex, treated with sodium iodide, was studied in in vitro experiments. Melipramine (5.10(-5)--10(-3)M) is shown to inhibit the K+-n-NFP-ase activity, competing with potassium ions. With pH changing from acid and neutral to alkaline values the inhibitory action of melipramine gains in intensity, whereas the protective effect of potassium ions declines. It is suggested that one of the mechanisms responsible for the inhibition of the K+-p-NFP-ase activity by melipramine is interaction of the inhibitor in the anionic sections of the enzyme complex.