Lucchelli A, Boselli C, Chiari M C, Grana E
Arch Int Pharmacodyn Ther. 1986 Feb;279(2):234-47.
The relaxing effect of dopamine on the rat isolated jejunum has been studied. Dopamine was found 170 times less potent than noradrenaline and 3 times more potent than tyramine. The relaxing effect of dopamine does not show the tachyphylaxis phenomenon, is present in preparations from rats pretreated with reserpine and is not influenced by cocaine. These results indicate that dopamine has a direct action. To characterize the receptor(s) through which dopamine causes intestinal relaxation the alpha-blocker phentolamine, the beta-blocker propranolol and the dopamine receptor blockers haloperidol and cis-alpha-flupenthixol, alone or in combination have been tested. 40% of inhibition of the response to dopamine was obtained with phentolamine, 25% with propranolol and 30% with haloperidol or cis-alpha-flupenthixol. Combining together three antagonists acting on three different receptors it was possible to obtain 70% of inhibition of the responses to dopamine. It is concluded that alpha and beta adrenoceptors and specific dopamine receptors are involved in the direct relaxing action of dopamine.
已对多巴胺对大鼠离体空肠的舒张作用进行了研究。发现多巴胺的效力比去甲肾上腺素低170倍，比酪胺高3倍。多巴胺的舒张作用不表现出快速耐受性现象，在用利血平预处理的大鼠制备物中存在，且不受可卡因影响。这些结果表明多巴胺具有直接作用。为了表征多巴胺引起肠道舒张所通过的受体，已单独或联合测试了α受体阻滞剂酚妥拉明、β受体阻滞剂普萘洛尔以及多巴胺受体阻滞剂氟哌啶醇和顺式α-氟哌噻吨。酚妥拉明使对多巴胺的反应抑制40%，普萘洛尔使抑制25%，氟哌啶醇或顺式α-氟哌噻吨使抑制30%。将作用于三种不同受体的三种拮抗剂联合使用，有可能使对多巴胺的反应抑制70%。得出的结论是，α和β肾上腺素能受体以及特定的多巴胺受体参与了多巴胺的直接舒张作用。
