Physiological and behavioral effects of chronic intracerebroventricular infusion of corticotropin-releasing factor in the rat

The present study was conducted to investigate the Long-term effects of chronic elevation of centrally circulating levels of corticotropin-releasing factor (CRF) on behavior and physiology. For this purpose ovine CRF was infused continuously far a period of 10 days into the lateral ventricle of rats with the aid of osmotic pumps (calculated CRF delivery was 4.9 mu g/day). Changes in daily rhythms in body temperature and home cage motor activity were recorded telemetrically during the infusion period. The most prominent physiological findings were a delayed body weight gain and a longlasting hyperthermia following CRF infusion. The peptide treatment furthermore increased adrenal weight and suppressed the weight of the thymus at the end of the experiment. Behaviorally, CRF administration elicited a short-lasting increase in activity during the light phase and an increased anxiety in an elevated plus-maze I week after the start of infusion. The similarities between the present results and the long-term changes previously described in behaviorally stressed rats indicate that chronically elevated Levels of CRF in the brain might play an important role in the induction and persistence of stress-related behavioral and physiological disorders. (C) 1997 Elsevier Science Ltd.