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本实验观察了可乐定对自家血恒速灌流的毁脑脊髓大鼠(pithed rat)后肢血管平滑肌的作用和该处突融后膜两种α受体亚型的存在。可乐定引起灌流压(PP)升高,呈剂量依赖关系,但效能远比选择性α_1受体激动剂苯福林低。对预先用利血平处理的大鼠,可乐定的作用被显著增强。高度选择性的α_1受体阻断剂哌唑嗪0.3mg/kg iv可部分阻断可乐定100μg ia的作用,增加哌唑嗪的剂量并不能进一步增加对可乐定的阻断作用。对于哌唑嗪不能阻断的部分,α_1受体阻断剂育亨宾却能表现出十分明显的抑制作用。这些结果提示在大鼠后肢血管平滑肌突触后膜上存在有α_1和α_2肾上腺素受体,但α_1受体似乎占优势。
In this study, we observed the effect of clonidine on vascular smooth muscle of the hind limbs of the cerebrospinal-rat (pithed rat) with constant blood flow perfusion at home and the existence of two α receptor subtypes after the sudden-thawing. Clonidine increased perfusion pressure (PP) in a dose-dependent manner, but its potency was far lower than that of the selective alpha-1 receptor agonist phenylephrine. The effect of clonidine was significantly enhanced in pre-reserpine-treated rats. Highly selective alpha 1 receptor blocker prazosin at 0.3 mg / kg iv partially blocked clonidine 100 μg ia, increasing prazosin dose did not further increase clonidine blockade. For prazosin can not block the part, α_1 receptor blocker yohimbine can show a very significant inhibitory effect. These results suggest that there are alpha 1 and alpha 2 adrenergic receptors on the postsynaptic membrane of rat hindlimb vascular smooth muscle, but the alpha 1 receptor appears to predominate.