Phentolamine stimulates insulin release and glucose clearance and suppresses food ingestion.
In Experiment One, phentolamine (PTA), an alpha-adrenergic blocker, was injected in rats at doses of 0, 50, 100, 200, and 300 micrograms/kg following a 4-hr fast. Measurement of food intake 1-hr postinjection revealed that 300 micrograms/kg PTA reduced food intake. Experiment Two evaluated the potential aversiveness of 300 micrograms/kg PTA. Four-hour fasted rats were adapted to a milk diet as the only food source during a 1-hr intake measurement period. After the 15-day adaptation period, three separate groups of animals (n = 8 per group) received the milk with cherry flavoring added and infections of either 1% body weight 0.9 NaCl, isosmotic LiCl or 300 micrograms/kg PTA. Only those subjects that had received LiCl injections developed a reliable aversion to the cherry-flavored milk. The final experiments subdivided the 1-hr feeding period into three 20-min segments and, in separate animals, food intake or plasma insulin and glucose changes were assessed. The animals were assigned to one of two groups receiving either 300 micrograms/kg PTA or equivolume 0.9% NaCl. PTA-injected subjects showed an immediate modest enhancement of insulin release during the first 20-min feeding segment following injection, compared to controls, while blood glucose levels decreased but never differed reliably between groups. Food intake was reliably suppressed in the second and third 20-min segments for the PTA-injected rats. We advance that PTA by enhancing glucose clearance may be reducing ingestion.
Barnett
C E
CE
Department of Psychology, Occidental College, Los Angeles, CA 90041.
Talbert
D R
DR
Vanderweele
D A
DA
D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects; D001786:Blood Glucose / Q000378:metabolism*; D001921:Brain / Q000187:drug effects*; D003214:Conditioning, Classical / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004326:Drinking / Q000187:drug effects; D004435:Eating / Q000187:drug effects*; D007328:Insulin / Q000097:blood*; D008297:Male; D010646:Phentolamine / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D013649:Taste / Q000187:drug effects
D001786:Blood Glucose; D007328:Insulin; D011942:Receptors, Adrenergic, alpha; D010646:Phentolamine