Examination of signalling pathways involved in muscarinic responses in bovine ciliary muscle using YM-254890, an inhibitor of the G q/11 protein

F. Yasui, M. Miyazu, A. Yoshida, K. Naruse, A. Takai

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Background and purpose: In the ciliary muscle, the tonic component of the contraction produced by cholinergic agonists is highly dependent on Ca 2+ provided by influx through non-selective cation channels (NSCCs) opened by stimulation of M 3 muscarinic receptors. We examined effects of YM-254890 (YM), a G q/11-specific inhibitor, on contraction, NSCC currents and [Ca 2+] i elevation induced by carbachol (CCh). Experimental approach: Isometric tension was recorded from ciliary muscle bundles excised from bovine eyes. In ciliary myocytes dispersed with collagenase and cultured for 1-5 days, whole-cell currents were recorded by voltage clamp and the intracellular free Ca 2+ concentration [Ca 2+] i was monitored using the Fluo-4 fluorophore. Existence and localization of M 3 receptors and the α subunit of G q/11 (Gα q/11) were examined by immunofluorescence microscopy using AlexaFluor-conjugated antibodies. Key results: Both phasic and tonic components of contractions evoked by 2 μM CCh were inhibited by YM (3-10 μM) in a dose-dependent manner. In the cultured cells, CCh (0.05-10 μM) evoked an NSCC current as well as an elevation of the [Ca 2+] i. Both initial and sustained phases of these CCh-evoked responses were abolished by YM (3-10 μM). Immunostaining of the cytoplasmic side of the plasma membrane of ciliary myocytes revealed a dense distribution of M 3 receptors and Gα q/11. Conclusions and implications: The tonic as well as phasic component of the ciliary muscle contraction appears to be under control of signals conveyed by a G q/11-coupled pathway. YM is a useful tool to assess whether G q/11 is involved in a signal transduction system.

Original languageEnglish
Pages (from-to)890-900
Number of pages11
JournalBritish Journal of Pharmacology
Volume154
Issue number4
DOIs
Publication statusPublished - Jun 21 2008

Keywords

  • Ciliary muscle
  • G inhibitor
  • GTP-binding proteins
  • Muscarinic agents
  • Visual accommodation

ASJC Scopus subject areas

  • Pharmacology

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