Conditioned insulin secretion and meal feeding in rats.

Previous researchers have reported that rats placed upon a feeding regimen such that they receive only 2 hrs of food/day (meal-fed rats) develop hyperinsulinemia at the time of the day associated with feeding, even in the absence of food. Controls fed ad lib show no such response. In the 3 experiments reported here, the 74 meal-fed Charles River rats had elevated insulin levels at only the specific time of the day associated with feeding, and the increment of insulin at that time could be eliminated with atropine. The 58 free-feeding controls, on the other hand, always had higher insulin levels than the meal-fed rats, did not have an elevation of insulin at the time of the day that the meal-fed rats normally ate, and had insulin values that were unaffected by atropine. Further experimentation showed that hyperinsulinemia could become associated with arbitrary stimuli always associated with eating for meal-fed rats. It is concluded that the hyperinsulinemia of meal-fed rats associated with their feeding time is a learned response. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)