Effects of corticotropin releasing factor on genetically obese (fatty) rats

Corticotropin releasing factor (CRF) has been administered into the third ventricle of lean and genetically obese Zucker fatty rats in both acute and chronic experiments. Following a single injection of CRF (5 micrograms or approximately 1 nmole) there was an acute reduction of food intake in both the lean and obese animals, but the effect was greater in the obese. This effect persisted for the first three hours but was no longer detectable in either lean or genetically obese animals at 6 hours. Binding of GDP to mitochondria from interscapular brown adipose tissue in 21-hour deprived animals was lower in the fatty rats than in the lean controls. The injection of CRF significantly increased GDP binding in both the lean and fatty rats. During chronic infusion of CRF into the third ventricle of fatty rats, there was a significant decrease in food intake in the obese rats and fall of body weight in both groups. The basal levels of GDP binding were significantly lower in the saline-infused fatty rats than in the saline-infused lean controls. The chronic infusion of CRF increased GDP binding in the fatty rats but not in the lean animals. The CRF-treated values for GDP binding in fatty rats however, remained significantly below the baseline values in the control animals. Chronic CRF infusion also significantly lowered glucose levels in the fatty rat. These studies are consistent with the hypothesis that CRF may be involved in the decreased food intake and increased sympathetic activity observed in genetically obese fatty rats following adrenalectomy.