The effects of two analogs of dopamine on ganglionic transmission in the sympathetic nervous system.

Two aminotetralin analogs of dopamine were studied for their effects on ganglionic transmission in the sympathetic nervous system. Nerve activity (spontaneous firing or evoked action potentials) was recorded on a preganglionic nerve (splanchnic), a mixed nerve (lumbar chain) and several postganglionic nerves (external carotid branch and renal nerve). 6,7-Dihydroxy-2-dimethylaminotetralin and 5,6-dihydroxy-2-dimethylaminotetralin were observed to markedly inhibit spontaneous firing in the renal nerve, external carotid branch and lumbar chain. Splanchnic nerve activity was unaltered, 6,7-Dihydroxy-2-dimethylaminotetralin also depressed evoked responses to submaximal stimulation in the external carotid branch and lumbar chain. These results suggest a ganglionic site of action. Since functional vasomotor activity in the isolated perfused canine forelimb in response to preganglionic nerve stimulation was unaltered, it was concluded that 6,7-dihydroxy-2-dimethylaminotetralin may depress transmission only at certain ganglionic pathways.