Docherty J R
Br J Pharmacol. 1984 May;82(1):15-23. doi: 10.1111/j.1476-5381.1984.tb16437.x.
The presynaptic cardio-inhibitory effects of the alpha-adrenoceptor agonists xylazine, cirazoline and amidephrine and their interaction with the antagonists yohimbine and prazosin were investigated in the pithed rat. The presynaptic inhibitory effects of the alpha 2-selective agonist xylazine were antagonized by the alpha 2-antagonist yohimbine but not by the alpha 1-antagonist prazosin, thus demonstrating the lack of alpha 2-adrenoceptor antagonism by prazosin. The presynaptic inhibitory effects of cirazoline were antagonized equally by yohimbine and prazosin, and the presynaptic inhibitory effects of the selective alpha 1-agonist amidephrine were antagonized by prazosin more potently than by yohimbine. In the nifedipine-treated isolated epididymal portion of the rat vas deferens, both xylazine and amidephrine produced concentration-dependent inhibition of the isometric contraction to single pulse electrical stimulation. The alpha 2-antagonist rauwolscine antagonized the inhibitory effects of xylazine but not of amidephrine . It is concluded that inhibitory alpha 1-adrenoceptors, as well as the already established alpha 2-receptors, are present presynaptically in the pithed rat heart and in the rat vas deferens.
在麻醉大鼠中研究了α-肾上腺素能受体激动剂赛拉嗪、西拉唑啉和酰胺福林的突触前心脏抑制作用及其与拮抗剂育亨宾和哌唑嗪的相互作用。α2选择性激动剂赛拉嗪的突触前抑制作用被α2拮抗剂育亨宾拮抗，但未被α1拮抗剂哌唑嗪拮抗，从而证明哌唑嗪缺乏α2肾上腺素能受体拮抗作用。西拉唑啉的突触前抑制作用被育亨宾和哌唑嗪同等拮抗，选择性α1激动剂酰胺福林的突触前抑制作用被哌唑嗪拮抗的效力比育亨宾更强。在硝苯地平处理的大鼠输精管离体附睾部分，赛拉嗪和酰胺福林均产生浓度依赖性抑制单脉冲电刺激引起的等长收缩。α2拮抗剂利血平拮抗赛拉嗪的抑制作用，但不拮抗酰胺福林的抑制作用。得出的结论是，抑制性α1肾上腺素能受体以及已确定的α2受体在麻醉大鼠心脏和大鼠输精管的突触前存在。
