[The effect of the antidepressant pyrazidol and its nitro analog on cGMP-dependent phosphodiesterase from the soluble fractions of the human cerebral cortex].

The effects of the antidepressant pyrazidol (pirlindole) and its nitro analog on cGMP-dependent phosphodiesterase from the soluble fraction of human brain cortex have been studied. Pirlindole inhibits the cGMP-induced activity of phosphodiesterase (IC50 = 1585 microM) without influencing the basal activity; its action is noncompetitive in respect of the substrate and the activator. Nitropirlindole is a more potent inhibitor of cGMP-dependent phosphodiesterase (IC50 = 115 microM) competing with the substrate for the catalytic site (K(i) = 70 microM). There is no direct interaction of pirlindole (pyrazidol) and its nitro analog with the cGMP-specific site in phosphodiesterase.