DIFFERENTIAL EFFECT OF VERAPAMIL ON NORADRENALINE, CARBACHOL, TYRAMINE AND 5-HYDROXYTRYPTAMINE INDUCED CONTRACTIONS OF THE RAT ANOCOCCYGEUS MUSCLE

  • 1 January 1982
    • journal article
    • research article
    • Vol. 259  (2) , 186-193
Abstract
The effect of verapamil and dantrolene sodium on the contractile responses evoked by noradrenaline [norepinephrine], carbachol, tyramine and 5-hydroxytryptamine on the rat anococcygeus muscle was studied. Dantrolene sodium did not significantly antagonize noradrenaline-, carbachol-, tyramine- and 5-hydroxytryptamine-induced contractions. Verapamil competitively antagonized 5-hydroxytryptamine-induced contractions, while non-competitive antagonism was observed with tyramine and carbachol. Noradrenaline-evoked contractions were unaffected. All agonists tested failed to produce a contraction in Ca2+-free medium, indicating that a transmembrane Ca2+ influx is involved in the contractile response to all these agonists. Evidently, there are verapamil-sensitive and verapamil-insensitive Ca channels in the rat anococcygeus muscle.

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