Tuncer M, Doğan N, Oktay S, Kayaalp S O
Arch Int Pharmacodyn Ther. 1985 Jul;276(1):17-27.
In order to characterize the 5-hydroxytryptamine (5-HT) receptors, the contractile effects of both 5-HT and alpha-adrenoceptor agonists were studied in helically-cut human umbilical artery and vein in the presence of different antagonists. Noradrenaline, phenylephrine and clonidine caused maximum contractions in vein amounting to only 9%, 14% and 11% of the maximum effect of 5-HT, respectively. The maximum effects of noradrenaline and phenylephrine in artery were only 18% and 29% of that of 5-HT. Clonidine failed to induce contractions in the artery. The alpha 1-adrenoceptor blocker, prazosin (1 X 10(-6) and 1 X 10(-5)M) did not antagonize 5-HT-induced contractions in the tissues studied. However, yohimbine, an alpha 2-adrenoceptor blocker, shifted the concentration-effect curves of the 5-HT to the right without any reduction in the maximum responses in both tissues. The pA2 values for yohimbine against 5-HT (6.46 and 6.72 in artery and vein, respectively) were different from the values for yohimbine against alpha 2-adrenoceptor agonists (8.2 and 8.6 against clonidine and M-7, respectively) in dog saphenous vein which contains postsynaptic alpha 2-adrenoceptors. 5-HT2 receptor antagonists, ketanserin (1 X 10(-7)-1 X 10(-6)M) and mianserin (1 X 10(-7)-1 X 10(-6)M) competitively antagonized 5-HT-induced contractions in both tissues. The pA2 values for ketanserin (7.89 and 7.86 in artery and vein, respectively) and mianserin (8.06 and 7.73 in artery and vein, respectively) were significantly lower than those obtained in other tissues which were shown to contain 5-HT2 receptors by the other authors. The results suggest that alpha-adrenoceptors play a minor role in 5-HT-induced contractions in both tissues. Yohimbine antagonized 5-HT action competitively, by blocking probably 5-HT receptors. The results also indicate that 5-HT receptors in human umbilical vessels are less sensitive to certain 5-HT2 antagonists than those of other tissues. A third subtype of 5-HT receptors different from the 5-HT1 and 5-HT2 receptors may be present in the human umbilical artery and vein.
为了表征5-羟色胺（5-HT）受体，在不同拮抗剂存在的情况下，研究了5-HT和α-肾上腺素能受体激动剂在螺旋切割的人脐动脉和静脉中的收缩作用。去甲肾上腺素、苯肾上腺素和可乐定在静脉中引起的最大收缩分别仅为5-HT最大效应的9%、14%和11%。去甲肾上腺素和苯肾上腺素在动脉中的最大效应仅为5-HT的18%和29%。可乐定未能在动脉中诱导收缩。α1-肾上腺素能受体阻滞剂哌唑嗪（1×10⁻⁶和1×10⁻⁵M）在研究的组织中未拮抗5-HT诱导的收缩。然而，α2-肾上腺素能受体阻滞剂育亨宾使5-HT的浓度-效应曲线向右移动，而两种组织中的最大反应均未降低。育亨宾对5-HT的pA2值（动脉和静脉中分别为6.46和6.72）与育亨宾对犬隐静脉中α2-肾上腺素能受体激动剂（分别为8.2和8.6，对可乐定和M-7）的pA2值不同，犬隐静脉含有突触后α2-肾上腺素能受体。5-HT2受体拮抗剂酮色林（1×10⁻⁷ - 1×10⁻⁶M）和米安色林（1×10⁻⁷ - 1×10⁻⁶M）竞争性拮抗两种组织中5-HT诱导的收缩。酮色林（动脉和静脉中分别为7.89和7.86）和米安色林（动脉和静脉中分别为8.06和7.73）的pA2值显著低于其他作者显示含有5-HT2受体的其他组织中的值。结果表明，α-肾上腺素能受体在两种组织中5-HT诱导的收缩中起次要作用。育亨宾通过可能阻断5-HT受体竞争性拮抗5-HT作用。结果还表明，人脐血管中的5-HT受体对某些5-HT2拮抗剂的敏感性低于其他组织中的受体。人脐动脉和静脉中可能存在不同于5-HT1和5-HT2受体的第三种5-HT受体亚型。
