title: The effects of serotonin precursors on the pressor response to intravenous clonidine in conscious rats.
abstract: 1. The interaction of the biosynthetic precursors of serotonin with the alpha-adrenoceptor-mediated pressor response to intravenous clonidine was investigated in unanaesthetized rats. 2. Pretreatment with 100 mg/kg of either L-tryptophan or 5-hydroxytryptophan (5-HTP) reduced the magnitude of the pressor response elicited by intravenous clonidine (25 microgram/kg) to 15% and 11%, respectively, of that observed in control rats. 3. The depression by L-tryptophan of the clonidine-induced pressor response could be prevented by pretreatment with either the L-aromatic amino acid decarboxylase inhibitor Rö44602 or the serotonin antagonist methysergide.
mesh_terms: D006916:5-Hydroxytryptophan / Q000494:pharmacology*; D000818:Animals; D001545:Benserazide / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects*; D003000:Clonidine / Q000494:pharmacology*; D004347:Drug Interactions; D008297:Male; D008784:Methysergide / Q000494:pharmacology; D051381:Rats; D012701:Serotonin / Q000096:biosynthesis*; D014364:Tryptophan / Q000494:pharmacology*
chemical_list: D012701:Serotonin; D001545:Benserazide; D014364:Tryptophan; D006916:5-Hydroxytryptophan; D003000:Clonidine; D008784:Methysergide