Doggrell S A
Gen Pharmacol. 1986;17(2):239-41. doi: 10.1016/0306-3623(86)90146-1.
The inhibitory effects of atropine and pirenzepine (nonselective and M1-selective antagonists, respectively) on the contractile responses of the epididymal half of the rat vas deferens to methacholine included a depression of the maximal response. In the presence of pirenzepine, atropine was a competitive antagonist of the responses to methacholine. However in the presence of atropine, pirenzepine remained a non-competitive inhibitor of the response. It is suggested that low concentrations of methacholine predominantly stimulate M2-receptors and that at high concentrations, methacholine also stimulates M1-receptors.
阿托品和哌仑西平（分别为非选择性拮抗剂和M1选择性拮抗剂）对大鼠输精管附睾段对乙酰甲胆碱收缩反应的抑制作用包括最大反应的降低。在哌仑西平存在的情况下，阿托品是对乙酰甲胆碱反应的竞争性拮抗剂。然而，在阿托品存在的情况下，哌仑西平仍然是该反应的非竞争性抑制剂。提示低浓度的乙酰甲胆碱主要刺激M2受体，而高浓度时，乙酰甲胆碱也刺激M1受体。
