Inhibition of reflex vagal bradycardia by a central action of 5-hydroxytryptophan.
1 Vagally mediated reflex bradycardia was elicited in spinal cats with intravenous pressor doses of noradrenaline. Administration of 5-hydroxytryptophan (1.5 and 3 mg total dose) into the fourth cerebral ventricle reduced the reflex bradycardia. 2 Inhibition of central amino acid decarboxylase with R044602 prevented the effects of 5-hydroxytryptophan. After intravenous administration of 5-hydroxytryptophan, vagal reflex bradycardia was not affected. 3 Results suggest that 5-hydroxytryptophan acts in the CNS to inhibit baroreceptor-mediated vagal reflex bradycardia and that action is mediated via conversion to 5-hydroxytryptamine.
D000818:Animals; D001545:Benserazide / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D003655:Decerebrate State / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects*; D007275:Injections, Intravenous; D007276:Injections, Intraventricular; D012701:Serotonin / Q000008:administration & dosage / Q000494:pharmacology*; D014630:Vagus Nerve / Q000502:physiology
D012701:Serotonin; D001545:Benserazide