The effects of chronic ventromedial hypothalamic stimulation on weight gain in rats.

The effects of chronic stimulation of the ventromedial hypothalamus and adjacent structures on body weight, food intake, and epididymal fat pad weight were examined in normophagic rats. Three hours of intermittent low level electrical stimulation were delivered three times per week for four weeks; body weight and food intake were monitored for an additional ten days after stimulation trials had ceased. Animals receiving ventromedial hypothalamic stimulation had the shallowest growth curves while stimulation of other structures produced a rate of growth that fell between that of the ventromedial hypothalamic and the implanted control group. This pattern persisted during the poststimulation phase. Food intake, while initially depressed in the stimulated groups, began to approach control levels by the third week of stimulation. Efficiency of food utilization (weight gain/consumption) was significantly reduced during the first week of stimulation in the ventromedial hypothalamic stimulated group. Fat pad weight was slightly decreased in this group as well. These findings suggest that chronic stimulation of the ventromedial hypothalamus causes a persistent shift in metabolic rate that results in a long-term inhibition of weight gain.