Excitatory 5-hydroxytryptamine receptors in the cat urinary bladder are of the M- and 5-HT2-type.
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.
Saxena
P R
PR
Heiligers
J
J
Mylecharane
E J
EJ
Tio
R
R
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002415:Cats; D003533:Cyproheptadine / Q000494:pharmacology; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D004347:Drug Interactions; D005260:Female; D006145:Guanethidine / Q000494:pharmacology; D007650:Ketanserin; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D010880:Piperidines / Q000494:pharmacology; D011985:Receptors, Serotonin / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D014326:Tropanes / Q000494:pharmacology; D001743:Urinary Bladder / Q000187:drug effects* / Q000502:physiology
D010880:Piperidines; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D014326:Tropanes; D003533:Cyproheptadine; D012701:Serotonin; D004246:Dimethylphenylpiperazinium Iodide; D001285:Atropine; D007650:Ketanserin; C042253:bemesetron; D008784:Methysergide; D006145:Guanethidine