Histochemical localization of adenylate cyclase in cultured sympathetic neurons

The catecholamine-stimulated adenylated cyclase activity was histochemically demonstrated at ultrastructural level in the cultured neurons of the sympathetic ganglia of the chick embryo. Adenylate cyclase activity was demonstrated in the axolemma of the axons and axon terminals, however not inside the axons. Heavy precipitates of the enzymatic reaction product was observed intracellularly in some cell processes identified as dendrites of the sympathetic neurons. In contrast to the extensive reaction in the neuropil, the reaction for the catecholamine-stimulated adenylate cyclase was scarse in the perikarya of the neurons. Only occasional spots of adenylate cyclase activity could be demonstrated in the plasmalemma of some neurons, and no reaction product was observed in the cytoplasm. No difference in the localization of the adenylate cyclase activity was observed when either dopamine or noradrenaline were used for stimulation. The possible roles of the catecholamine-stimulated adenylate cyclase in the function of the interneuronal connections between the aminergic neurons of the sympathetic ganglion are discussed.