Involvement of corticotropin-releasing factor in the anorexia induced by exercise.

The role of corticotropin-releasing factor (CRF) in the sex-dependent anorexia induced by exercise was investigated in male Wistar rats. Each rat was implanted with a permanent guide cannula that was stereotaxically positioned close to the right lateral ventricle of the brain. During the recovery period, which lasted 10 days, rats were accustomed to eat three meals per day. The onset of each meal occurred every 8 hours. During a meal, rats were allowed free access to a pelleted stock diet for one hour. Ten days after the surgery, rats were injected in the right lateral ventricle of the brain with either saline or 100 micrograms of alpha-helical CRF (9-41), a selective CRF antagonist. Fifteen minutes after the injections, half of the rats were forced to exercise while the others were allowed to rest. The exercise consisted of a moderately intense period of running on a motor-driven treadmill during 40 minutes. Immediately after the period of exercise, animals were offered food, and the amount eaten during the meal period was carefully measured. The results indicate that the exercised rats ate less food than resting animals when saline was infused prior to subjecting the animals to running. In addition, in saline-treated animals, growth of exercised rats was slower than that of resting rats during the day following exercise. Contrastingly, in rats infused with alpha-helical CRF (9-41) exercise exerted no effect on food intake, neither did it reduce body weight gain of the rats. The present results suggest that CRF plays a major role in the anorexia caused by exercise in male rats.