Santicioli P, Zagorodnyuk V, Renzetti A R, Maggi C A
Menarini Ricerche, Firenze, Italy.
Naunyn Schmiedebergs Arch Pharmacol. 1999 May;359(5):420-7. doi: 10.1007/pl00005370.
We have analyzed, by the sucrose gap method, the action of otilonium bromide, a quaternary ammonium derivative in use for the symptomatic therapy of irritable bowel syndrome, on the electrical and mechanical responses initiated by different stimuli in the circular muscle of the guinea-pig proximal colon. Otilonium bromide produced a concentration-dependent inhibition of membrane depolarization (IC50 4.1 microM), action potentials (APs) and contraction (IC50 3.7 microM) produced by the muscarinic receptor agonist, methacholine. It also produced a concentration-dependent inhibition of APs and accompanying contraction (IC50 31 microM) produced by KCl (30 mM), and had a biphasic effect on the cholinergic excitatory junction potential (e.j.p.) produced by single pulse electrical field stimulation: at low concentrations (0.1-0.3 microM) otilonium bromide enhanced the e.j.p. and, at higher concentrations (IC50 22 microM and 16 microM toward depolarization and contraction), produced a concentration-dependent inhibition. Otilonium bromide eliminated the APs superimposed on the depolarization induced by the tachykinin NK1 receptor agonist, [Sar9]substance P-sulphone and suppressed the corresponding contraction (IC50 43 microM) but had little effect on the sustained membrane depolarization induced by this agonist. On the other hand, otilonium bromide produced a similar inhibitory effect on both membrane depolarization and contraction (IC50 38 microM and 45 microM, respectively) induced by the tachykinin NK2 receptor agonist [betaAla8]neurokinin A (4-10). When tested in the presence of nifedipine (1 microM), otilonium bromide had no effect on the membrane depolarization induced by [Sar9]substance P-sulphone but inhibited in a concentration-dependent manner the depolarization induced by [betaAla8]neurokinin A (4-10) (IC50 41 microM). In contrast, the blocker of receptor-operated cation channels, SKF 96365, inhibited with similar potency the depolarization induced by both [Sar9]substance P-sulphone and [betaAla8]neurokinin A (4-10) (IC50 60 microM and 54 microM, respectively). In radioligand binding experiments otilonium bromide produced a concentration-dependent inhibition of the binding of both an agonist ([125I]neurokinin A, Ki 7.2 microM) and an antagonist ([3H]SR 48968, Ki 2.2 microM) to membranes of Chinese hamster ovary cells transfected with the human tachykinin NK2 receptor. In conclusion, the present findings demonstrate that, in the microM range of concentrations, otilonium bromide acts as a muscarinic and tachykinin NK2 receptor antagonist and as a calcium channel blocker. The latter property is likely to account for its ability to suppress contraction initiated by the tachykinin NK1 receptor agonist. Therefore multiple mechanisms of action account for the ability of otilonium bromide to reduce stimulated motility of intestinal smooth muscle.
我们采用蔗糖间隙法，分析了用于肠易激综合征症状治疗的季铵衍生物奥替溴铵，对豚鼠近端结肠环行肌中不同刺激引发的电反应和机械反应的作用。奥替溴铵对毒蕈碱受体激动剂乙酰甲胆碱产生的膜去极化（IC50为4.1微摩尔）、动作电位（APs）和收缩（IC50为3.7微摩尔）呈现浓度依赖性抑制作用。它对氯化钾（30毫摩尔）产生的APs和伴随的收缩（IC50为31微摩尔）也有浓度依赖性抑制作用，并且对单脉冲电场刺激产生的胆碱能兴奋性接头电位（e.j.p.）有双相作用：在低浓度（0.1 - 0.3微摩尔）时，奥替溴铵增强e.j.p.，而在较高浓度（对去极化和收缩的IC50分别为22微摩尔和16微摩尔）时，产生浓度依赖性抑制。奥替溴铵消除了速激肽NK1受体激动剂[Sar9]P物质 - 砜诱导的去极化上叠加的APs，并抑制了相应的收缩（IC50为43微摩尔），但对该激动剂诱导的持续膜去极化影响很小。另一方面，奥替溴铵对速激肽NK2受体激动剂[βAla8]神经激肽A（4 - 10）诱导的膜去极化和收缩（IC50分别为38微摩尔和45微摩尔）产生类似的抑制作用。在硝苯地平（1微摩尔）存在下进行测试时，奥替溴铵对[Sar9]P物质 - 砜诱导的膜去极化无影响，但以浓度依赖性方式抑制[βAla8]神经激肽A（4 - 10）诱导的去极化（IC50为41微摩尔）。相反，受体操纵性阳离子通道阻滞剂SKF 96365以相似的效力抑制[Sar9]P物质 - 砜和[βAla8]神经激肽A（4 - 10）诱导的去极化（IC50分别为60微摩尔和54微摩尔）。在放射性配体结合实验中，奥替溴铵对激动剂（[125I]神经激肽A，Ki为7.2微摩尔）和拮抗剂（[3H]SR 48968，Ki为2.2微摩尔）与转染了人速激肽NK2受体的中国仓鼠卵巢细胞膜的结合均产生浓度依赖性抑制。总之，目前的研究结果表明，在微摩尔浓度范围内，奥替溴铵作为毒蕈碱和速激肽NK2受体拮抗剂以及钙通道阻滞剂发挥作用。后一种特性可能解释了其抑制速激肽NK1受体激动剂引发的收缩的能力。因此，多种作用机制解释了奥替溴铵降低肠道平滑肌刺激运动性的能力。
