Sahyoun H A, Costall B, Naylor R J
J Pharm Pharmacol. 1982 May;34(5):318-24. doi: 10.1111/j.2042-7158.1982.tb04715.x.
Catecholamine control of circular smooth muscle activity of the lower oesophageal (LOS) and pyloric sphincters (PS) of the guinea-pig was studied using alpha- and beta-adrenoceptor agonists and antagonists. In both sphincters dopamine (DA) and noradrenaline (NA) caused relaxation followed by contraction of the circular smooth muscle, although the ability of NA to contract the PS was weak and inconsistent. Isoprenaline relaxed both sphincter preparations but, whilst phenylephrine contracted the muscle of the PS, it caused a biphasic relaxation-contraction of the LOS. The use of the alpha- and beta-adrenoceptor antagonists, phentolamine and propranolol, indicated that contractions of both sphincters by NA and DA involved an alpha-type adrenoceptor whilst relaxation was mediated via a beta-adrenoceptor (PS) or via both alpha- and beta-adrenoceptors (LOS). Use of the alpha 1 and alpha 2 antagonists, prazosin and yohimbine, indicated that the alpha-adrenoceptor type involved with both the contractions and relaxation was alpha 1. Both domperidone and haloperidol antagonized the contractile responses of both tissues to DA (and partly the relaxation of the LOS) but were similarly effective against the contractions induced by NA and phenylephrine; an effect on alpha 1-adrenoceptors was therefore, concluded. In selectively antagonizing the contractile effects of DA in the PS, domperidone enhanced DA's ability to relax this sphincter.
利用α和β肾上腺素能受体激动剂及拮抗剂，研究了豚鼠下食管括约肌（LOS）和幽门括约肌（PS）环形平滑肌活动的儿茶酚胺控制。在这两种括约肌中，多巴胺（DA）和去甲肾上腺素（NA）均可引起环形平滑肌先舒张后收缩，尽管NA使PS收缩的能力较弱且不稳定。异丙肾上腺素使两种括约肌标本均舒张，而苯肾上腺素使PS的肌肉收缩，但使LOS产生双相性舒张-收缩。使用α和β肾上腺素能拮抗剂酚妥拉明和普萘洛尔表明，NA和DA引起的两种括约肌收缩均涉及α型肾上腺素能受体，而舒张是通过β肾上腺素能受体（PS）或通过α和β肾上腺素能受体（LOS）介导的。使用α1和α2拮抗剂哌唑嗪和育亨宾表明，参与收缩和舒张的α肾上腺素能受体类型为α1。多潘立酮和氟哌啶醇均拮抗两种组织对DA的收缩反应（以及部分拮抗LOS的舒张），但对NA和苯肾上腺素诱导的收缩同样有效；因此得出对α1肾上腺素能受体有作用的结论。在选择性拮抗DA对PS的收缩作用时，多潘立酮增强了DA使该括约肌舒张的能力。
