Comparison of the cardiovascular responses to intracerebroventricular administration of tryptamine, 5-hydroxytryptamine, tryptophan and 5-hydroxytryptophan in rats.
General characteristics of the cardiovascular responses to intracerebroventricular (i.c.v.) injection of tryptamine, 5-hydroxytryptamine (5-HT), tryptophan and 5-hydroxytryptophan (5-HTP) were compared. Relatively small doses of tryptamine and 5-HT (0.005-0.1 microM) produced considerable, long-lasting and dose-dependent pressor effects, which sometimes were followed by prolonged depressor effects. Tryptophan (0.02-0.5 microM) and 5-HTP (0.02-0.2 microM) caused variable and usually slight, but long-lasting, vascular responses or no vascular response A large dose of tryptamine (0.5 microM) evoked variable vascular effects, while the same dose of 5-HT and 5-HTP evoked marked and prolonged depressor effects. The vascular responses to the drugs were accompanied by variable changes in heart rate. Tryptamine, 5-HT and 5-HTP, in the majority of rats, produced a bradycardia. The present study provides evidence that the cardiovascular response to i.c.v. administration of tryptamine is similar to that of 5-HT, supporting the idea that tryptamine, in addition to 5-HT, participates in the central physiological regulation of the rat cardiovascular system. The role of tryptophan and 5-HTP by themselves in this regulation, if any is of secondary importance.
D006916:5-Hydroxytryptophan / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D007276:Injections, Intraventricular; D008297:Male; D051381:Rats; D012701:Serotonin / Q000008:administration & dosage / Q000494:pharmacology*; D014363:Tryptamines / Q000008:administration & dosage / Q000494:pharmacology*; D014364:Tryptophan / Q000008:administration & dosage / Q000494:pharmacology*
D014363:Tryptamines; D012701:Serotonin; C030820:tryptamine; D014364:Tryptophan; D006916:5-Hydroxytryptophan