EXCITATORY 5‐HYDROXYTRYPTAMINE RECEPTORS IN THE CAT URINARY BLADDER ARE OF THE M‐AND 5‐HT₂‐TYPE

Abstract

In anaesthetized cats, a biphasic contraction of the urinary bladder, consisting of an initial spike followed by a longer-lasting contracture, was elicited by 5-hydroxytryptamine (5-HT) in doses of 3-30 micrograms/kg, i.a. Administration of MDL 72222 (30, 100 and 300 micrograms/kg, i.v.), which specifically antagonizes the M-type 5-HT receptors, selectively blocked the spike phase of the 5-HT response. Ketanserin (30, 100 and 300 micrograms/kg, i.v.), on the other hand, eliminated only the second phase of the 5-HT-induced bladder contraction. Injection of MDL 72222 (300 micrograms/kg) after ketanserin (300 micrograms/kg), or of 100 micrograms/kg of methysergide or cyproheptadine, or 300 micrograms/kg of ketanserin after MDL 72222 (300 micrograms/kg), led to blockade of both phases of the response to 5-HT. The contractile response to dimethylphenylpiperazinium (DMPP) remained unaffected. These results clearly show that the early and late phases of the cat urinary bladder contraction elicited by 5-HT are mediated by M and 5-HT2 receptors, respectively.

Influence of 5‐hydroxytryptamine and the effect of a new serotonin receptor antagonist (sarpogrelate) on detrusor smooth muscle of streptozotocin‐induced diabetes mellitus in the rat *

“…15 Clinical studies have demonstrated that ketanserin significantly increases maximum and mean urinary flow rates and significantly decreases urethral pressure. 16 However, ketanserin partially blocks a 1 -adrenergic receptors.…”

An examination of 5‐hydroxytryptamine receptors in human saphenous vein

“…In the periphery, 5-HT is a potent vasoconstrictor in many vascular beds, but the constriction seems to involve two distinct receptor subtypes: contractions to 5-HT in the rabbit aorta, rat aorta, rat tail artery and dog femoral artery are mediated by 5-HT2-receptors at which ketanserin is a potent and competitive antagonist (Humphrey, 1984;Peroutka, 1984); contractions in the dog saphenous vein and human and dog basilar arteries are mediated by 5-HT1 or 5-HTI-like receptors (Peroutka, 1984;Feniuk et al, 1985). However, no selective antagonist is available for characterization of these 5-HT,-like receptors, and indeed the phrase 5-HT,-like has also been used to describe the 5-HT receptors mediating vasodilatation (Marwood & Stokes, 1984), tachycardia (Saxena et al, 1985) and inhibition of transmitter release (Fozard, 1984a).…”

5-Hydroxytryptamine Receptors, Especially the 5-HT4 Receptor, in Guinea Pig Urinary Bladder

“…In vitro study has shown that 5-HT causes contractions of urinary bladder preparations from several mammals (5). In most species, activation of 5-HT 2 receptor has been reported to cause contractions due to direct stimulation of smooth muscle cells of cat (6,7) and human (8) urinary bladder. Activation of 5-HT 3 receptor causes neurogenic contractions mediated by stimulation of the receptor located on the excitatory neurons in the cat (7), mouse (9), guinea pig (10), rabbit (11,12), and human (13,14).…”