Prins N H, Shankley N P, Welsh N J, Briejer M R, Lefebvre R A, Akkermans L M, Schuurkes J A
Department of Gastrointestinal Pharmacology, Janssen Research Foundation, Beerse, Belgium.
Br J Pharmacol. 2000 Apr;129(8):1601-8. doi: 10.1038/sj.bjp.0703254.
Recently, it was demonstrated that 5-HT induces relaxation of human colon circular muscle through activation of 5-HT(4) receptors and 5-HT(7) receptors. The aim of the current study was to develop a new in vitro bioassay of human colon that would facilitate the pharmacological analysis of 5-HT responses mediated solely by 5-HT(4) receptors. Contracting circular muscle strips with KCl (80 mM) yielded a stable contractile tension and, in contrast to muscarinic cholinoceptor agonists and histamine, a profound reduction of spontaneous contractility. This allowed the establishment of reproducible, fully-defined, agonist concentration-response curves by cumulative dosing. Under these conditions, 5-HT induced a concentration-dependent relaxation (pEC(50) 7.31, Hill slope 0.91). Neither methysergide (10 microM) nor granisetron (1 microM) affected the 5-HT-induced relaxation, suggesting that 5-HT(1), 5-HT(2), 5-HT(3), 5-ht(5), 5-HT(6) or 5-HT(7) receptors are not involved. The lack of effect of tetrodotoxin (0.3 microM) indicated a direct effect of 5-HT on the smooth muscle. The selective 5-HT(4) receptor antagonists GR 113808, GR 125487 and RS 39604 competitively antagonized the 5-HT-induced relaxation (pK(B) 9.43, 10.12 and 8.53, respectively). SB 204070 (1 nM) produced a rightward shift (pA(2) 10.34) and depression of the 5-HT curve. These affinity estimates are similar to those previously reported for 5-HT(4) receptors. The selective 5-HT(4) receptor agonists, prucalopride and R076186, induced relaxations (pEC(50) 7.50 and 7.57, respectively), that were blocked by GR 113808 (3 nM), yielding pA(2) estimates of 9.31 and 9.21, respectively. To summarise, in KCl (80 mM)-contracted muscle strips, 5-HT induces relaxation through activation of a homogeneous smooth muscle 5-HT(4) receptor population. This new bioassay allows the focused, pharmacological characterization of human colonic 5-HT(4) receptors in vitro.
最近的研究表明，5-羟色胺（5-HT）通过激活5-HT（4）受体和5-HT（7）受体诱导人结肠环行肌松弛。本研究的目的是开发一种新的人结肠体外生物测定法，以促进对仅由5-HT（4）受体介导的5-HT反应进行药理学分析。用氯化钾（80 mM）收缩环行肌条可产生稳定的收缩张力，与毒蕈碱型胆碱能受体激动剂和组胺不同，它能显著降低自发收缩性。这使得通过累积给药建立可重复的、完全确定的激动剂浓度-反应曲线成为可能。在这些条件下，5-HT诱导浓度依赖性松弛（pEC（50）7.31，希尔斜率0.91）。麦角新碱（10 microM）和格拉司琼（1 microM）均不影响5-HT诱导的松弛，这表明5-HT（1）、5-HT（2）、5-HT（3）、5-ht（5）、5-HT（6）或5-HT（7）受体未参与其中。河豚毒素（0.3 microM）无作用表明5-HT对平滑肌有直接作用。选择性5-HT（4）受体拮抗剂GR 113808、GR 125487和RS 39604竞争性拮抗5-HT诱导的松弛（pK（B）分别为9.43、10.12和8.53）。SB 204070（1 nM）使5-HT曲线右移（pA（2）10.34）并压低。这些亲和力估计值与先前报道的5-HT（4）受体的估计值相似。选择性5-HT（4）受体激动剂普芦卡必利和R076186诱导松弛（pEC（50）分别为7.50和7.57），均被GR 113808（3 nM）阻断，pA（2）估计值分别为9.31和9.21。总之，在氯化钾（80 mM）收缩的肌条中，5-HT通过激活均匀的平滑肌5-HT（4）受体群体诱导松弛。这种新的生物测定法允许在体外对人结肠5-HT（4）受体进行有针对性的药理学表征。
