Elliott J
Department of Veterinary Basic Sciences, Royal Veterinary College, London, UK.
J Vet Pharmacol Ther. 1997 Aug;20(4):308-17. doi: 10.1046/j.1365-2885.1997.00078.x.
Rings of equine digital vein examined under conditions of isometric tension recording constricted to alpha-adrenoceptor agonists with an order of potency of 5-bromo-6-[2-imidazolin-2-yl-amino]-quinoxaline bitartrate (UK 14304) = noradrenaline > 6-Allyl-2-amino-5,6,7,8-tetrahydro-4H-thiazolo-(4,5-d) azepine (BHT-920) > phenylephrine > dopamine > methoxamine. The maximum force generated was greatest for the non-selective agonist noradrenaline and lowest for the alpha2-selective agonist BHT-920 with the other agonists between these two extremes. Selective inactivation of alpha1-adrenoceptors (achieved by treating yohimbine-protected tissues with phenoxybenzamine) reduced the maximum responses of all agonists, the EC50 values of UK 14304, BHT-920 and noradrenaline and increased the EC50 values of phenylephrine and methoxamine. Prazosin (30 nM) had no inhibitory effect on responses to low concentrations of BHT-920 and UK 14304 and caused competitive inhibition of responses to phenylephrine and noradrenaline giving pKb values of 8.49 +/- 0.18 and 8.23 +/- 0.14, respectively. Yohimbine (0.1 microM) caused significant competitive inhibition of responses to BHT-920 and noradrenaline with calculated pKb values of 8.43 +/- 0.11 for BHT-920 and 7.43 +/- 0.31 for noradrenaline and non-competitive inhibition of responses to UK 14304. 2-[2-methoxy-1,4-benzodioxan-2-yl]-2-imidazoline (RX 821002; 10 nM) caused competitive inhibition of responses to BHT-920 (pKb 9.04 +/- 0.27) and dopamine (pKb 8.2 +/- 0.2). These data indicate that equine digital veins possess both post-synaptic alpha1 and alpha2-adrenoceptors.
在等长张力记录条件下对马趾静脉环进行研究，该静脉环对α - 肾上腺素能受体激动剂产生收缩反应，其效力顺序为5 - 溴 - 6 - [2 - 咪唑啉 - 2 - 基 - 氨基] - 喹喔啉酒石酸盐（UK 14304）=去甲肾上腺素＞6 - 烯丙基 - 2 - 氨基 - 5,6,7,8 - 四氢 - 4H - 噻唑并[4,5 - d]氮杂䓬（BHT - 920）＞去氧肾上腺素＞多巴胺＞甲氧明。非选择性激动剂去甲肾上腺素产生的最大张力最大，α2选择性激动剂BHT - 920产生的最大张力最小，其他激动剂产生的最大张力介于这两者之间。α1 - 肾上腺素能受体的选择性失活（通过用酚苄明处理育亨宾保护的组织来实现）降低了所有激动剂的最大反应、UK 14304、BHT - 920和去甲肾上腺素的EC50值，并增加了去氧肾上腺素和甲氧明的EC50值。哌唑嗪（30 nM）对低浓度BHT - 920和UK 14304的反应无抑制作用，对去氧肾上腺素和去甲肾上腺素的反应产生竞争性抑制，其pKb值分别为8.49±0.18和8.23±0.14。育亨宾（0.1 microM）对BHT - 920和去甲肾上腺素的反应产生显著的竞争性抑制，BHT - 920的计算pKb值为8.43±0.11，去甲肾上腺素的计算pKb值为7.43±0.31，对UK 14304的反应产生非竞争性抑制。2 - [2 - 甲氧基 - 1,4 - 苯并二恶烷 - 2 - 基] - 2 - 咪唑啉（RX 821002；10 nM）对BHT - 920（pKb 9.04±0.27）和多巴胺（pKb 8.2±0.2）的反应产生竞争性抑制。这些数据表明马趾静脉同时具有突触后α1和α2 - 肾上腺素能受体。
