Wang J Y, Don J J, Liu K H, Chen H I
Department of Physiology, National Defense Medical Center, Taipei.
Chin J Physiol. 1993;36(2):71-8.
Experiments were designed to characterize the effects mediated by alpha-1 and alpha-2 adrenoceptors in saphenous and femoral veins of the cat. Ring segments of saphenous and femoral veins were mounted for isometric tension recording in modified Krebs-bicarbonate solution, gassed with 95% O2-5% CO2 and maintained at 37 degrees C. Norepinephrine (a mixed alpha 1 and alpha 2 agonist), phenylephrine (a preferential alpha 1 agonist) and clonidine (a preferential alpha 2 agonist) caused dose (concentration)-dependent contractions in saphenous and femoral veins. The maximal contractions produced by clonidine were significantly less than those produced by norepinephrine or phenylephrine in both veins. However, threshold dose and EC50 values indicated that clonidine was more potent than norepinephrine and phenylephrine. Contractile responses to these agonists were attenuated when the veins were pretreated with alpha 1-or alpha 2-adrenoceptor antagonists, prazosin and yohimbine, respectively. The contractile responses to norepinephrine and tyramine were inhibited to a greater extent by yohimbine than by prazosin in both saphenous and femoral veins, suggesting that norepinephrine released from perivascular nerve terminals activates preferentially postsynaptic alpha 2-adrenoceptors. Further examination of alpha-adrenoceptor subtypes was achieved by comparing pA2 values of prazosin and yohimbine from Arunlakshana and Schild plots. Chronic sympathetic denervation by removing lumbar sympathetic chain significantly reduced the contractile responses evoked by tyramine. Denervation did not significantly affect the concentration-response curve to phenylephrine but significantly augmented the contractile responses evoked by clonidine in both veins.(ABSTRACT TRUNCATED AT 250 WORDS)
实验旨在表征α-1和α-2肾上腺素能受体在猫隐静脉和股静脉中介导的效应。将隐静脉和股静脉的环形节段安装在改良的 Krebs-碳酸氢盐溶液中进行等长张力记录，用95% O2-5% CO2 通气并维持在37摄氏度。去甲肾上腺素（一种α1和α2混合激动剂）、苯肾上腺素（一种优先的α1激动剂）和可乐定（一种优先的α2激动剂）在隐静脉和股静脉中引起剂量（浓度）依赖性收缩。在两条静脉中，可乐定产生的最大收缩明显小于去甲肾上腺素或苯肾上腺素产生的最大收缩。然而，阈剂量和EC50值表明可乐定比去甲肾上腺素和苯肾上腺素更有效。当静脉分别用α1-或α2-肾上腺素能受体拮抗剂哌唑嗪和育亨宾预处理时，对这些激动剂的收缩反应减弱。在隐静脉和股静脉中，育亨宾对去甲肾上腺素和酪胺收缩反应的抑制程度均大于哌唑嗪，这表明从血管周围神经末梢释放的去甲肾上腺素优先激活突触后α2-肾上腺素能受体。通过比较来自阿伦拉克沙纳和希尔德图的哌唑嗪和育亨宾的pA2值，进一步研究了α-肾上腺素能受体亚型。通过切除腰交感神经链进行慢性交感神经去神经支配显著降低了酪胺引起的收缩反应。去神经支配对苯肾上腺素的浓度-反应曲线没有显著影响，但显著增强了两条静脉中可乐定引起的收缩反应。（摘要截断于250字）
