| Abstract: | To determine whether central insulin administration lowers the level around which body weight is regulated, insulin (6 mU/day) or saline was infused into the 3rd ventricles of 4 groups of rats. One insulin-infused and 1 saline-infused group were food-deprived for 3 days and were then returned to an ad lib feeding schedule. The other 2 groups were maintained on ad lib feeding throughout. Insulin-infused food-deprived rats lost weight at a significantly greater rate than saline-infused food-deprived rats. In ad lib fed rats, insulin infusion caused a significant reduction of food intake and weight relative to saline-infused controls. When formerly food-deprived rats were returned to ad lib feeding, they gained weight, and this was significantly more pronounced in the saline-infused than the insulin-infused group. The body weights of the two insulin-infused groups converged on a value approximately 9% below the average of the 2 saline infused groups. Findings suggest that the 3rd-ventricular infusion of insulin does not incapacitate the rats and that they can alter their food intake either upward or downward to attain a new weight. Results also support the hypothesis that direct administration of insulin into the brain determines the level of weight maintained by the animal. (PsycINFO Database Record (c) 2010 APA, all rights reserved) |
