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Receptors mediating the effects of 5‐hydroxytryptamine on the tracheal vasculature and smooth muscle of sheep
Author(s) -
Webber S.E.,
Salonen R.O.,
Widdicombe J.G.
Publication year - 1990
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1990.tb14647.x
Subject(s) - ketanserin , methysergide , 5 ht receptor , vascular smooth muscle , endocrinology , medicine , receptor , serotonin , agonist , vasoconstriction , receptor antagonist , muscle contraction , chemistry , biology , antagonist , smooth muscle
1 The effects of 5‐hydroxytryptamine (5‐HT) and the selective 5‐HT 3 receptor agonist 2‐methyl‐5‐HT were examined on the tracheal vasculature in anaesthetised, paralysed and artificially ventilated sheep. The cranial tracheal arteries were perfused with blood at constant flow and perfusion pressure was measured. 5‐HT and 2‐methyl‐5‐HT were injected into the arterial perfusate. Changes in tracheal smooth muscle tone were also measured. 2 5‐HT contracted the tracheal smooth muscle. This contraction was not affected by the 5‐HT 2 receptor antagonist ketanserin, but was blocked by the combined ‘5‐HT 1 ‐like’ and 5‐HT 2 receptor antagonist methysergide. 2‐methyl‐5‐HT had no effect on the tracheal smooth muscle. 3 5‐HT had a complex action on the tracheal vasculature producing either a biphasic change (vasoconstriction followed by dilatation) or just a constriction. 2‐methyl‐5‐HT had a weak vasoconstrictor effect. 4 The vasoconstrictions produced by 5‐HT and 2‐methyl‐5‐HT were blocked by ketanserin. The vasodilatation produced by 5‐HT was resistant to ketanserin but was antagonised by methysergide. 5 Thus 5‐HT contracts the tracheal smooth muscle of sheep by stimulating ‘5‐HT 1 ‐like’ receptors. 5‐HT constricts the tracheal vascular bed by stimulating 5‐HT 2 receptors or dilates the vascular bed by stimulating ‘5‐HT 1 ‐like’ receptors. 5‐HT 3 receptors appear not to be involved in the responses of the tracheal vasculature or smooth muscle to 5‐HT.