Leff A R, Tallet J, Munoz N M, Shoulberg N
J Appl Physiol (1985). 1986 Jan;60(1):216-24. doi: 10.1152/jappl.1986.60.1.216.
We studied the simultaneous alpha- and beta-adrenergic response characteristics of canine tracheal smooth muscle in 398 strips from 67 dogs in vitro. Experiments were performed to determine the effects of beta-adrenergic blockade on the expression of the alpha-adrenoceptor contractile responses elicited by norepinephrine (NE), phenylephrine (PE), and clonidine (CLO). Maximal active tension caused by NE increased from 39.1 +/- 27.0 to 241 +/- 75.0 g/cm2 as the concentration of propranolol (PROP) was increased from 10(-6) to 10(-4) M. Augmentation of tracheal smooth muscle contraction caused by PE and CLO was also observed with progressive beta-adrenoceptor blockade; contraction to NE, PE, and CLO was blocked selectively with 3 X 10(-5) M phentolamine (PA) and phenoxybenzamine (PBZ). The beta-adrenergic relaxing properties of the same three agonists were also studied. After alpha-adrenergic blockade with PA or PBZ, all three agonists caused relaxation (NE greater than CLO greater than PE) of methacholine-induced contraction of tracheal smooth muscle that was reversed selectively with PROP. We demonstrate that NE, PE, and CLO cause simultaneous stimulation of both the alpha- and beta-adrenergic receptors in tracheal smooth muscle; the net response elicited is the result of adrenergic physiological antagonism and depends on the relative degree of alpha- and/or beta-adrenoceptor blockade.
我们在体外对67只犬的398条气管平滑肌条进行研究，观察其α和β肾上腺素能的同时反应特性。进行实验以确定β肾上腺素能阻滞剂对去甲肾上腺素（NE）、苯肾上腺素（PE）和可乐定（CLO）引起的α肾上腺素能受体收缩反应表达的影响。随着普萘洛尔（PROP）浓度从10^(-6) M增加到10^(-4) M，NE引起的最大主动张力从39.1±27.0 g/cm²增加到241±75.0 g/cm²。随着β肾上腺素能阻滞剂的逐步增加，PE和CLO引起的气管平滑肌收缩也增强；用3×10^(-5) M酚妥拉明（PA）和酚苄明（PBZ）可选择性阻断对NE、PE和CLO的收缩反应。还研究了相同三种激动剂的β肾上腺素能舒张特性。在用PA或PBZ进行α肾上腺素能阻断后，所有三种激动剂均引起气管平滑肌对乙酰甲胆碱诱导的收缩的舒张（NE＞CLO＞PE），且PROP可选择性逆转这种舒张。我们证明，NE、PE和CLO可同时刺激气管平滑肌中的α和β肾上腺素能受体；所引发的净反应是肾上腺素能生理拮抗作用的结果，并且取决于α和/或β肾上腺素能受体阻断的相对程度。
