Gunst S J, Stropp J Q, Flavahan N A
Division of Thoracic Diseases and Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905.
J Appl Physiol (1985). 1987 Aug;63(2):514-20. doi: 10.1152/jappl.1987.63.2.514.
Concentration-response curves for norepinephrine, acetylcholine, and 5-hydroxytryptamine were obtained in vitro alone and after precontraction with histamine, 5-hydroxytryptamine, or acetylcholine. Responses obtained to each agonist after precontraction were greater than responses to the agonist alone after subtraction of the force due to the precontracting stimulus. Augmentation of responses after precontraction was the greatest for norepinephrine, less for 5-hydroxytryptamine, and least for acetylcholine. Verapamil had no significant effect on the augmentation of responses to either 5-hydroxytryptamine or acetylcholine caused by precontraction. When the efficacy of acetylcholine was decreased by receptor alkylation with phenoxybenzamine, the augmentation of responses to acetylcholine caused by precontraction with histamine was significantly enhanced. Differences in the magnitude of the effect of precontraction on responses to different agonists may reflect differences in their efficiency of stimulus-response coupling in canine tracheal smooth muscle, or they may result from an increased expression of distinct receptors or receptor-mediated effects uncovered by the facilitory stimuli.
分别在体外单独以及在组胺、5-羟色胺或乙酰胆碱预收缩后，获得去甲肾上腺素、乙酰胆碱和5-羟色胺的浓度-反应曲线。预收缩后对每种激动剂的反应，在减去预收缩刺激产生的张力后，大于单独对该激动剂的反应。预收缩后反应增强，对去甲肾上腺素最为明显，对5-羟色胺次之，对乙酰胆碱最小。维拉帕米对预收缩引起的5-羟色胺或乙酰胆碱反应增强无显著影响。当用酚苄明使乙酰胆碱受体烷基化从而降低其效能时，组胺预收缩引起的乙酰胆碱反应增强显著增强。预收缩对不同激动剂反应的影响程度差异，可能反映了犬气管平滑肌中它们刺激-反应偶联效率的差异，也可能是由于促进性刺激揭示了不同受体或受体介导效应的表达增加所致。
