Matsumoto S, Nagayama T, Kanno T, Yamasaki M, Shimizu T
Department of Physiology, Fukushima Medical College, Japan.
J Auton Nerv Syst. 1995 Jun 25;53(2-3):126-36. doi: 10.1016/0165-1838(94)00168-j.
We investigated to determine whether or not the inhibitory M2-receptors function in the rabbit lung and heart. Rabbits were anesthetized, vagotomized, paralyzed and ventilated. Administration of gallamine, an M2-receptor antagonist, augmented an increase of PT produced by vagal stimulation with or without simultaneous administration of histamine and the increases were dose-dependent. Conversely, prior treatment with pilocarpine, an M2-receptor agonist, reduced these responses in a dose-dependent manner. The PT responses to histamine injection only were not significantly altered by administration of either gallamine or pilocarpine. The remaining bronchoconstrictor responses to the three stimuli in the presence of gallamine or pilocarpine were completely blocked by atropine. In another series of experiments, gallamine treatment enhanced bronchoconstriction evoked by vagal stimulation but reduced acetylcholine (ACh)-induced bronchoconstriction. These opposite responses were dose-dependent for gallamine. The results suggest that there are inhibitory M2-receptors in the parasympathetic nerves innervating the lungs in the rabbit. Furthermore, gallamine treatment that completely blocked bradycardia evoked by ACh administration reduced vagally-mediated bradycardia. This implies that gallamine appears to have an antagonistic action on muscarinic receptors in the rabbit heart.
我们进行了研究，以确定抑制性M2受体在兔肺和心脏中是否发挥作用。将兔子麻醉、切断迷走神经、使其麻痹并进行通气。给予M2受体拮抗剂加拉明后，无论是否同时给予组胺，迷走神经刺激所产生的肺顺应性增加都会增强，且这种增加呈剂量依赖性。相反，预先用M2受体激动剂毛果芸香碱治疗，可剂量依赖性地降低这些反应。单独注射组胺时的肺顺应性反应，无论给予加拉明还是毛果芸香碱，均无明显改变。在加拉明或毛果芸香碱存在的情况下，对三种刺激的其余支气管收缩反应可被阿托品完全阻断。在另一系列实验中，加拉明治疗增强了迷走神经刺激诱发的支气管收缩，但降低了乙酰胆碱（ACh）诱导的支气管收缩。加拉明的这些相反反应呈剂量依赖性。结果表明，在支配兔肺的副交感神经中存在抑制性M2受体。此外，完全阻断ACh给药所诱发的心动过缓的加拉明治疗，降低了迷走神经介导的心动过缓。这意味着加拉明似乎对兔心脏中的毒蕈碱受体具有拮抗作用。
