Frazier Elfaridah P, Braverman Alan S, Peters Stephan L M, Michel Martin C, Ruggieri Michael R
Department of Pharmacology and Pharmacotherapy, University of Amsterdam, The Netherlands.
J Pharmacol Exp Ther. 2007 Sep;322(3):998-1002. doi: 10.1124/jpet.107.125393. Epub 2007 Jun 27.
Muscarinic acetylcholine receptors, particularly M(3) receptors, are physiologically the most important mechanism to induced urinary bladder smooth muscle contraction. Their prototypical signaling response is a stimulation of phospholipase C (PLC), and this also has been shown in the urinary bladder. Nevertheless, it has remained controversial whether PLC signaling mediates bladder contraction induced by muscarinic receptor agonists. Studies in favor and against a role for PLC differed in their experimental protocol (single versus repeated concentration-response curves within a single preparation) and in the PLC inhibitors that have been used. We have now tested whether previous differential conclusions regarding a role for PLC are related to inhibitors and/or experimental protocols. In a single curve protocol, U-73,122 [1-[6-[((17beta)-3-methoxyestra-1,3,5[10]-trien-17-yl)amino]hexyl]-1H-pyrrole-2,5-dione] did not attenuate carbachol responses. In a repeated curve protocol, ET-18-OCH(3) (1-O-octadecyl-2-O-methyl-sn-glycero-3-phosphorylcholine) lacked significant inhibition relative to vehicle time controls. In contrast, D609 (O-tricyclo[5.2.1.02,6]dec-9-yl dithiocarbonate potassium salt) depressed maximal carbachol effects but also nonspecifically inhibited contraction induced by KCl. Neomycin did not affect the carbachol-induced rat urinary bladder contraction. We conclude that previously reported differences relate to the use of inhibitors rather than experimental protocols and that the overall data do not support a role for PLC in M(3) muscarinic receptor-mediated rat bladder contraction.
毒蕈碱型乙酰胆碱受体，尤其是M(3)受体，在生理上是诱导膀胱平滑肌收缩的最重要机制。它们典型的信号转导反应是刺激磷脂酶C（PLC），这在膀胱中也已得到证实。然而，PLC信号转导是否介导毒蕈碱受体激动剂诱导的膀胱收缩仍存在争议。支持和反对PLC起作用的研究在实验方案（单个制剂内的单次与重复浓度-反应曲线）以及所使用的PLC抑制剂方面存在差异。我们现在测试了先前关于PLC作用的不同结论是否与抑制剂和/或实验方案有关。在单曲线方案中，U-73,122 [1-[6-[((17β)-3-甲氧基雌甾-1,3,5[10]-三烯-17-基)氨基]己基]-1H-吡咯-2,5-二酮]并未减弱卡巴胆碱反应。在重复曲线方案中，相对于溶媒时间对照，ET-18-OCH(3)（1-O-十八烷基-2-O-甲基-sn-甘油-3-磷酸胆碱）缺乏显著抑制作用。相比之下，D609（O-三环[5.2.1.02,6]癸-9-基二硫代碳酸钾盐）降低了卡巴胆碱的最大效应，但也非特异性地抑制了氯化钾诱导的收缩。新霉素不影响卡巴胆碱诱导的大鼠膀胱收缩。我们得出结论，先前报道的差异与抑制剂的使用有关，而非实验方案，并且总体数据不支持PLC在M(3)毒蕈碱受体介导的大鼠膀胱收缩中起作用。
