Feed efficiency in growth-retarded rats with ventromedial and dorsomedial hypothalamic lesions produced shortly after weaning

Abstract

Weanling male rats received electrolytic lesions (L) in the ventromedial (VMN) and dorsomedial (DMN) hypothalamic nuclei; sham-operated rats served as controls. The animals were maintained for various periods up to 50 postoperative days on lab chow under standard conditions. In a short-term study, food intake and body weights were measured daily and body weight gain was divided by the food eaten to obtain the efficiency of food utilization. Also, gains in metabolic size ( kg 3 4 ) were divided by food eaten. Both manipulations showed that DMNL rats, except for the first two postoperative days, utilized food normally. The same changes were obtained for weanling VMNL rats, except that they did not show a decline in utilization during the first two postoperative days. Computation of efficiency of food utilization for both VMNL and DMNL rats over postoperative durations ranging from 7 to 50 days showed that among 12 out of 14 experiments DMNL rats utilized food as well as controls. Out of 8 experiments, rats with VMNL utilized food better for weight gained than controls in one and poorer than controls also in one experiment; in reference to metabolic size they utilized food normally. The foregoing data, gathered from 225 DMNL, 64 VMNL and 181 control rats show quite convincingly that food utilization in both types of experimental animals is unimpaired despite profound reductions in ponderal and linear growth and food intake in the DMNL rat and reduced circulating growth hormone levels in the VMNL rat.