L-5-Hydroxytryptophan-induced drinking in rats: possible mechanisms for induction.
Administration of L-5-hydroxytryptophan (25 mg/kg body weight, SC) to female rats resulted in copious drinking. The dipsogenic response to administration of L-5-hydroxytryptophan (5-HTP) was blocked by propranolol (6 mg/kg body weight, IP), a beta-adrenergic antagonist, and captopril (35 mg/kg body weight, IP), an angiotensin converting enzyme inhibitor. In addition, clonidine (12.5 and 25 microgram/kg body weight, IP), a central alpha-adrenergic agonist known to inhibit renin release, attenuated drinking during 1, 2 and 3 hours after 5-HTP was administered. These results suggest that 5-HTP-induced drinking is mediated by way of the renin-angiotensin system. Haloperidol (150 microgram/kg body weight, IP), a dopaminergic antagonist, also attenuated the dipsogenic response to administration of 5-HTP. In addition, incremental reductions in 5-HTP-induced drinking with increasing doses of spiperone (37.5 to 150 microgram/kg body weight, IP), a more potent dopaminergic antagonist, were demonstrated. Thus, the dipsogenic response to administration of 5-HTP to rats is dependent on both the renin-angiotensin system and an intact dopaminergic pathway.
D006916:5-Hydroxytryptophan / Q000494:pharmacology*; D000818:Animals; D002216:Captopril / Q000494:pharmacology; D003000:Clonidine / Q000494:pharmacology; D004326:Drinking / Q000187:drug effects*; D004347:Drug Interactions; D005260:Female; D006220:Haloperidol / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D013134:Spiperone / Q000494:pharmacology; D013268:Stimulation, Chemical
D013134:Spiperone; D002216:Captopril; D011433:Propranolol; D006916:5-Hydroxytryptophan; D006220:Haloperidol; D003000:Clonidine