Evidence for a circulating ergostatic factor: studies on parabiotic rats.

The effect of electrolytic ventromedial hypothalamic lesions or forced overfeeding through gastric cannulas was studied in parabiotic rats. In one experiment a ventromedial hypothalamic lesion in one member of the parabiotic union was associated with an increased fatness in the lesioned rat and a decrease in fat pad weight and a rise in body density (loss of fat) of the unlesioned animal. In the other two experiments a high fat or high carbohydrate diet was tube fed to one member of a parabiotic union. The average preinfusion intake per rat was 56 kcal/day. When 90 kcal/day were given through the intragastric cannula, oral intake of calories for the two animals fell to approximately 44 kcal/day. Body fat of the non-tube-fed animal was less than in the tube-fed controls. These studies suggest the presence of an ergostatic (energy stabilizing) factor that enters and is transported in the blood with passage from one animal to another.