兔输卵管平滑肌的肾上腺素受体与收缩活性

本文以离体兔输卵管平滑肌制备,比较输卵管各部(峡部和壶腹部)环肌和纵肌的肾上腺素受体效应及性激素状态的影响。经雌激素处理的兔输卵管峡部环肌和纵肌,对肾上腺素(Adr)、去甲肾上腺素(NA)和苯肾上腺素(PEP)均能产生浓度依赖性收缩反应,α-受体阻断剂则能对抗之。三种激动剂的pD_2值,顺序为Adr>NA>PEP。三种受体阻断剂对抗NA在兔输卵管峡部平滑肌引起收缩效应的pA_2值,顺序为酚妥拉明(Phen)≥哌唑嗪(Praz)>育亨宾(yoh)。β-受体阻断剂心得宁不影响Adr、NA和PEP所产生的收缩效应;心得安则对上述激动剂的兴奋效应具有明显非特异性抑制作用。孕激素处理的兔输卵管平滑肌,对不同浓度NA的收缩反应(包括E_(Amax))以及NA的pD_2值,均较雌激素处理组为低。提示孕激素可能降低α-激动剂与兔输卵管肾上腺素受体的亲和力,和/或减少受体数目。

ADRENOCEPTORS AND CONTRACTILITY OF OVIDUCTAL SMOOTH MUSCLE IN RABBITS

Adrenaline, noradrenaline and phenylephrine induced contraction of both the circular and the longitudinal muscles of the isthmus in a dose-dependent manner in estrogen treatedrabbits. The responses of oviductal smooth muscle to noradrenaline were competitivelyantagonized by α-adrenergic blockers, phentolamine, prazosine and yohimbine. Thesefindings confirmed the presence of α-excitatory adrenoceptors in the rabbit oviduct. Theorder of pD_2 values for adrenergic agonists were adrenaline>noradrenaline>phenyleph-rine. The order of pA_2 values for α-adrenergic antagonists antagonizing the contractileeffect of noradrenaline on the isthmic smooth muscle were phentolamine≥prazosine>yohimbine. β-blocker, practolol, did not affect the contractile effect induced by adrenaline, no-radrenaline or phenylephrine. However, propranolol, non-specifically inhibited the ex-citatory effect induced by the above agonists. The responses of the oviduct to α-adrenergic agonists were shown to be influencedby the hormonl status of the animals. The contractile responses of the oviduct from megestrol acetate treated rabbits to noradrenaline, and the pD_2 values for noradrenalinewere smaller than those of oviducts from estradiol treated rabbits. These suggest thatprogestogen might reduce the affinity of α-adrenergic agonists to combine with theadrenoceptors, and/or reduce the number of adrenergic receptors. Estrogen has theconverse effects.