Direct influence of antidepressants on GTP binding protein of adenylate cyclase in cell membranes of the cerebral cortex of rats.

Recently, it has been suggested that antidepressant drugs exert their pharmacological action through functional changes in the adrenergic-receptor coupled adenylate cyclase system. In the present research, we examined the direct effects of antidepressants on adenylate cyclase (A-cyclase) activity by in vitro incubation of cell membranes from the cerebral cortex of rats with these drugs. All antidepressants examined, such as imipramine, clomipramine, amitriptyline, desipramine, mianserin and zimelidine inhibited A-cyclase in a dose dependent manner. Antidepressants did not exert any influence on Mn2+-induced elevation of A-cyclase, but significantly suppressed F(-)-stimulated A-cyclase activity. GTP-induced elevation of A-cyclase was completely inhibited by prior incubation with antidepressants. Our conclusion, therefore, is that antidepressants may reduce A-cyclase activity not by inhibiting the function of the catalytic unit of A-cyclase, but by suppressing the N-protein function.