Muscarinic Receptor Subtypes Mediating Ca2+ Sensitization of Intestinal Smooth Muscle Contraction: Studies with Receptor Knockout Mice

作者：Suguro Mayuko; Matsuyama Hayato^*; Tanahashi Yasuyuki; Unno Toshihiro; Kitazawa Takio; Yamada Masahisa; Komori Seiichi

来源：Journal of Veterinary Medical Science, 2010, 72(4): 443-451.

DOI：10.1292/jvms.09-0458

• Ca2+ sensitization
• intestinal smooth muscle
• knockout mouse
• M-3 subtype
• muscarinic receptor

In the present study, we have characterized muscarinic receptor subtypes that mediate carbachol-induced Ca2+ sensitization of contraction in intestinal smooth muscle, using mutant mice lacking M-2 or M-3 muscarinic receptors or both receptor subtypes. In alpha-toxin-permeabilized muscle strips from wild-type (WT) mice, isometric tension responses to Ca2+ applied cumulatively (pCa 7.0-5.0) were increased when the muscarinic against carbachol (100 mu M) was added to the medium, as judged from shifts of pCa-tension curves in both 50% effective concentration (EC50) and maximum response (E-max) of pCa-tension curve. In preparations from M-2-knockout (KO) mice, pCa-tension curves were also shifted by carbachol (100 mu M), and the extents of the EC50 and E-max changes resembled those observed in preparations from WT mice. In preparations from M-3-KO or M-2/M-3-double KO mice, however, no significant changes in pCa-tension curves were obtained after carbachol application. The G(q/11)-type G-protein inhibitor YM-254890 (1 mu M) completely blocked the Ca2+ sensitization of contraction induced by carbachol in M-2-KO or WT preparations. The results strongly support the idea that the muscarinic net of Ca2+ sensitization in intestinal smooth muscles is mediated by the M-3 muscarinic receptor coupled to G(q/11)-type G-proteins, without any significant involvement or the other muscarinic receptor subtypes including M-2.

• 出版日期2010-4