Treatment with alpha-helical-CRF(9-41) prevents the anorectic effect of 17-beta-estradiol

The role of corticotropin-releasing factor (CRF) in the anorexia induced by 17-beta-estradiol (E2) has been assessed in castrated female rats that were trained to eat their daily food ration in three separate meals. Each rat was implanted with a permanent guide cannula that was aimed at the right lateral ventricle of the brain. Seven days after the brain surgery each rat was also subcutaneously implanted with an osmotic minipump containing Buserelin, a potent GnRH agonist that induces reversible castration in rats. Eight rats were used in the study, and each of them underwent four experimental treatments that consisted of a) a subcutaneous (SC) injection of oil combined with an intracerebroventricular (ICV) infusion of saline, b) a SC injection of E2 combined with an ICV infusion of saline c) a SC injection of oil combined with an ICV infusion of alpha-helical CRF(9-41), and d) a SC injection of E2 combined with an ICV injection of alpha-helical CRF(9-41). Subcutaneous injections of E2 or oil were carried out the day before the ICV infusions of alpha-helical CRF(9-41) or saline. Intracerebroventricular infusions were performed 30 min before the meal for which the interaction effect of E2 and alpha-helical CRF(9-41) on food intake was determined. E2 and alpha-helical CRF(9-41) interacted on food intake; E2 brought about a 33% reduction in food intake in rats when infused with saline, whereas it was without effect when infused with alpha-helical-CRF(9-41)-treated rats. The present results provide evidence that CRF is involved in the anorectic effect of E2.