| Abstract: | In helical strips of monkey cerebral and mesenteric arteries contracted with prostaglandin F2 alpha, dopamine in low concentrations produced a moderate relaxation but in high concentrations produced a contraction from the level of relaxation. On the other hand, coronary, renal, and femoral arterial strips responded to dopamine with only a concentration-dependent contraction. Treatment with phenoxybenzamine or phentolamine potentiated the dopamine-induced relaxation seen in cerebral and mesenteric arteries and reversed the contraction in the other arteries to a relaxation. After treatment with phenoxybenzamine, relaxant responses to dopamine of cerebral, mesenteric, and renal arteries were almost identical, and, compared with those, the responses of coronary and femoral arteries were appreciably less. Relaxations induced by dopamine were not influenced by propranolol, atropine, aminophylline, cimetidine, and aspirin but were markedly attenuated by droperidol. Adenosine-induced relaxations were not affected by droperidol. It is concluded that dopamine preferentially relaxes monkey cerebral and mesenteric arteries, possibly via dopaminergic receptors. It appears that the dopamine-induced contractions mediated by alpha-adrenoceptors predominate over the relaxation in coronary, renal, and femoral arteries, and dopaminergic receptor function is greater in cerebral, mesenteric, and renal arteries than in coronary and femoral arteries. |
