Food-motivated performance in rats with ventromedial hypothalamic lesions: Effects of body weight, deprivation, and preoperative training

Abstract

The effects of body weight, level of deprivation, and preoperative training upon the performance of hyperphagic rats with ventromedial hypothalamic (VMH) lesions were investigated. In Expt 1, nonobese VMH rats responded at control levels on a VI 1-min food reinforcement schedule under deprived and nondeprived testing conditions, whereas obese VMH rats showed a performance decrement only under the deprived testing conditions. Although the effect of preoperative training failed to reach significance, the differences were in the predicted direction. In Expt 2, obese VMH rats displayed a greater finickiness to quinine-adulterated water than did nonobese VMH rats and control rats only during deprived testing conditions. There were no differences in quinine solution intakes among the groups under the nondeprived testing condition. It was concluded that VMH lesions per se do not produce a decrease in food-motivated performance, but that the performance deficits are a function of the body weight of the animal and the level of deprivation at the time of testing.