DIRECT AND INDIRECT ACTIONS OF 5-HYDROXYTRYPTAMINE IN THE RAT ANOCOCCYGEUS MUSCLE

  • 1 January 1981
    • journal article
    • research article
    • Vol. 254  (1) , 13-19
Abstract
The contractile effect of 5-hydroxytryptamine [5-HT] on the rat isolated anococcygeus muscle was analyzed. 5-HT (10-6-1.6 .times. 10-5 g/ml) concentration-dependently contracted the anococcygeus muscle. The contractions were not competitively antagonized by methysergide (2.5 .times. 10-8-10-6 g/ml), as the contractile response to higher concentrations of 5-HT were not much reduced. The methysergide-resistant contractions to 5-HT were not reduced by hyoscine (6 .times. 10-7 g/ml) or tetrodotoxin (2 .times. 10-7 g/ml), but were completely abolished by phentolamine (3 .times. 10-7 g/ml). 5-HT-induced contractions were considerably reduced but not completely abolished by reserpinization. 5-HT contracted the rat anococcygeus muscle directly (by activating tryptaminergic D receptors) and indirectly by releasing noradrenaline [norepinephrine] at the nerve endings.

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