Corticotropin-releasing factor and schedule-induced polydipsia

Two experiments examined the effects of ICV-administered corticotropin-releasing factor (CRF) and alpha-helical CRF (9-41), a CRF antagonist, on the performance of schedule-induced polydipsia (SIP). Infusions of CRF into the lateral ventricle dose-dependently (0.02, 0.1, and 0.5 micrograms) attenuated both the volume of water consumed and licking on a fixed-time 60-s schedule. This effect of CRF on schedule-induced drinking was accompanied by a reduction in the number of nose pokes made into the food tray, suggesting that CRF may attenuate SIP through an action on appetitive motivation. Neither the temporal distribution of responding nor the locomotor activity induced by the schedule was affected by CRF. In marked contrast to these effects of exogenous CRF on the performance of SIP, infusions of alpha-helical CRF (1, 5, and 25 micrograms) into the lateral ventricle did not affect the performance of schedule-induced polydipsia. The implications of these results for the hypothesis that SIP is a coping response to stress are discussed.