[Effects of dopamine and dobutamine on vascular smooth muscles].

The effects of dopamine and dobutamine on mechanical responses of the mesenteric artery and ear artery of the rabbit were investigated. Dopamine elicited no contraction in the mesenteric artery, but inhibited contractions evoked by excess concentrations of K+ or norepinephrine. In contrast, in the ear artery, dopamine induced contractions in concentrations exceeding 0.7 microM. Dobutamine did not induce contractions either in the mesenteric artery or ear artery, but inhibited contractions evoked by excess concentrations of K+ or norepinephrine in both tissues. Moreover, dobutamine in concentrations over 10 nM inhibited contractions induced by dopamine in the ear artery. These results indicated that regional differences were apparent in the effects of dopamine on vascular tissues and that dobutamine possessed vasodilating effects. The inhibitory effects of dobutamine on contractions induced by dopamine in the rabbit ear artery suggested a possible clinical benefit of dobutamine for maintaining peripheral circulation during combined use of dopamine and dobutamine.