Sahyoun H A, Costall B, Naylor R J
J Pharm Pharmacol. 1982 Jun;34(6):381-5. doi: 10.1111/j.2042-7158.1982.tb04734.x.
Circular smooth muscle strips taken from the body region of the guinea-pig stomach responded to dopamine and noradrenaline with contraction at lower concentrations followed by relaxation at higher concentrations. A beta-adrenoceptor-mediated relaxation response was excluded by propranolol treatment and this allowed the remaining alpha-adrenoceptor involvement with relaxation and contraction to be incisively differentiated in terms of two distinct alpha-adrenoceptor mechanisms. Thus, the relaxation responses to the catecholamines were mimicked by phenylephrine and antagonized by prazosin, phentolamine but not by yohimbine or rauwolscine. In contrast, the catecholamine-induced contractions were mimicked by clonidine and antagonized by yohimbine and phentolamine but not by prazosin. It is therefore concluded that the alpha mechanisms via which dopamine and noradrenaline are able to relax and contract the circular smooth muscle from the body region of guinea-pig stomach are of the alpha 1- and alpha 2-type respectively.
取自豚鼠胃体部的环形平滑肌条对多巴胺和去甲肾上腺素的反应是，低浓度时收缩，高浓度时松弛。普萘洛尔处理排除了β-肾上腺素能受体介导的松弛反应，这使得剩余的α-肾上腺素能受体参与的松弛和收缩能够根据两种不同的α-肾上腺素能受体机制进行明确区分。因此，苯肾上腺素模拟了对儿茶酚胺的松弛反应，哌唑嗪、酚妥拉明可拮抗该反应，而育亨宾或萝芙木碱则不能。相反，可乐定模拟了儿茶酚胺诱导的收缩反应，育亨宾和酚妥拉明可拮抗该反应，而哌唑嗪则不能。因此得出结论，多巴胺和去甲肾上腺素通过其使豚鼠胃体部环形平滑肌松弛和收缩的α机制分别属于α1型和α2型。
