The effects of idazoxan and other alpha 2-adrenoceptor antagonists on food and water intake in the rat.
1. Idazoxan (1, 3, 10 mg kg-1, i.p.) produced a significant increase in food and water intake in freely feeding rats during the daylight phase. 2. The more selective and specific alpha 2-adrenoceptor antagonists, RX811059 (0.3, 1, 3 mg kg-1, i.p.) and RX821002 (0.3, 1, 3 mg kg-1, i.p.), did not produce hyperphagia in rats, however, the highest dose produced a significant increase in water intake. 3. The peripherally acting alpha 2-adrenoceptor antagonist, L-659,066 (1, 3, 10 mg kg-1, i.p.), did not affect food intake in the 4 h following injection, but the highest dose (10 mg kg-1), produced a large increase in water intake. 4. These results indicate that alpha 2-adrenoceptor antagonists may increase water intake by a peripherally mediated mechanism. 5. The lack of effect RX811059 and RX821002 on food intake contrasts with the large dose-related increases induced by idazoxan and suggests that the hyperphagic effects of idazoxan are not due to alpha 2-adrenoceptor blockade but may instead reflect its affinity for a non-adrenoceptor site, a property not shared by the other alpha 2-antagonists.
Department of Pharmacology, School of Medical Sciences, University Walk, Bristol.
H C
HC
Jackson
I J
IJ
Griffin
D J
DJ
Nutt
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D004146:Dioxanes / Q000378:metabolism / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004326:Drinking / Q000187:drug effects*; D004435:Eating / Q000187:drug effects*; D019329:Idazoxan / Q000031:analogs & derivatives; D008297:Male; D011807:Quinolizines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011955:Receptors, Drug / Q000187:drug effects / Q000378:metabolism
D000317:Adrenergic alpha-Antagonists; D004146:Dioxanes; D011807:Quinolizines; D011955:Receptors, Drug; C055732:vatinoxan; C065483:ethoxyidazoxan; C058525:2-methoxyidazoxan; D019329:Idazoxan