Mediation of 5-hydroxytryptamine-induced tachycardia in the pig by the putative 5-HT4 receptor.
Intravenous bolus injections of 5-hydroxytryptamine (5-HT; 3, 10 and 30 micrograms kg-1), 5-methoxytryptamine (5-MeO-T; 3, 10 and 30 micrograms kg-1), renzapride (BRL 24924; 3, 10, 30 and 100 micrograms kg-1) and isoprenaline (0.03, 0.1 and 0.3 micrograms kg-1) to anaesthetized pigs increased heart rate by, respectively, 22 +/- 3, 44 +/- 3 and 65 +/- 4 beats min-1 (5-HT; n = 17); 12 +/- 1, 26 +/- 2 and 44 +/- 4 beats min-1 (5-MeO-T; n = 15), 5 +/- 2, 11 +/- 2, 18 +/- 4 and 37 +/- 5 beats min-1 (renzapride; n = 8) and 17 +/- 2, 46 +/- 3 and 75 +/- 3 beats min-1 (isoprenaline; n = 13). The responses to 5-HT, 5-MeO-T and renzapride were antagonized by ICS 205-930 (1 and 3 mg kg-1, i.v.), which did not modify the increases in heart rate by isoprenaline. Renzapride showed tachyphylaxis and attenuated the responses to 5-HT. These findings indicate that 5-HT elicits tachycardia in the pig by acting on a novel receptor, either similar or identical to the 5-HT4 receptor identified in mouse brain colliculi.
Villalón
C M
CM
Department of Pharmacology, Faculty of Medicine and Health Sciences, Erasmus University Rotterdam, The Netherlands.
den Boer
M O
MO
Heiligers
J P
JP
Saxena
P R
PR
D000758:Anesthesia; D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D001921:Brain / Q000378:metabolism; D001643:Bridged Bicyclo Compounds / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic; D006321:Heart / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects*; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D009206:Myocardium / Q000378:metabolism*; D011985:Receptors, Serotonin / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology*; D013552:Swine; D000077526:Tropisetron
D001549:Benzamides; D001643:Bridged Bicyclo Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D007211:Indoles; D011985:Receptors, Serotonin; D012701:Serotonin; D000077526:Tropisetron; C053006:renzapride; D007545:Isoproterenol