REDUCTION OF FOOD-INTAKE IN RATS BY INTRAPERITONEAL INJECTION OF LOW-DOSES OF AMYLIN

The effect of amylin injected IP on food intake in rats of different a ge (7-9 weeks, 3 months, 15-18 months) was investigated. The possible site of amylin action was investigated using vagotomized rats. Lastly, the influence of food composition on amylin's effect was investigated . In 12-h food-deprived old rats, food intake was decreased significan tly by amylin (1-10 mu g/kg) when injected at the beginning of the dar k phase. Although the anorectic effect of amylin occurred somewhat ear lier at 10 mu g/kg, no clear dose-response relationship was observed. The anorectic effect was most marked in the first 2 h after amylin inj ection and was compensated over 24 h. Amylin (1 and 5 mu g/kg) did not reduce food intake in undeprived old rats. In young rats, amylin (0.1 -1 mu g/kg) dose-dependently reduced food intake if rats were food-dep rived for 24 h, but not when deprived for 12 h. Dissection of the comm on hepatic vagus branch did not block the anorectic effect of amylin ( age of rats: 3 months). The effect tended to last longer in vagotomize d rats. The anorectic effect of amylin did not depend on the presence of carbohydrates in the diet. Water intake was not affected by amylin in water-deprived rats. In conclusion, the anorectic effect of amylin was observed at much lower doses (minimal effective dose: 0.5 mu g/kg) than reported before. These doses are similar to anorectic doses of c holecystokinin, a physiological peripheral satiety agent.