Electron microscopical demonstration of adenylate cyclase activity in nervous tissue

Adenylate cyclase (EC4.6.1.1) activity stimulated by norepinephrine and dopamine was demonstrated histochemically by electron microscopy in the cerebral cortex and caudate nucleus of the rat. The precipitating agent in the histochemical reaction was cobalt, which was shown biochemically to increase the adenylate cyclase activity. The reaction product was located in the synapses, being contiguous attached to the postsynaptic membrane. It was also located in the plasma membrane of some nerve fibers. Alloxan, the specific inhibitor of adenylate cyclase, inhibited the reaction in the cerebral cortex and caudate nucleus, and haloperidol had a somewhat similar effect in the caudate region.