ESTROUS CYCLE-RELATED AND ACUTE STRESS-RELATED CHANGES OF RAT OVARIANIMMUNOREACTIVE CORTICOTROPIN-RELEASING FACTOR

Corticotropin-releasing factor (CRF), the major regulator of the stres s response within the central nervous system, is also present at the p eripheral sites, including the gonads, and the gene encoding its own r eceptor can be finely induced in selective ovarian compartments in bot h control and stressful conditions during the gonadal life cycle. The present study, therefore, investigated the influence of both gonadal f unction and estrous cycle on the immunoreactive CRF (irCRF) contents i n the immature and adult rat ovary. In addition, the effect of an acut e (5 min) or chronic intermittent (twice a day for 4 days) cold swimmi ng stress on ovarian irCRF contents was evaluated. High-performance li quid chromatography (HPLC), gel-chromatography (Sephadex G-75, 45 x 1 cm) and a direct radioimmunoassay were performed to measure irCRF ovar ian contents. The HPLC elution profile of irCRF in ovarian tissues of adult rats was superimposable on that of synthetic rat/human CRF and g el-chromatograms performed according to the phase of the estrous cycle revealed higher irCRF contents at proestrus. Total irCRF ovarian cont ent was undetectable both in control and acute stressed immature rats, while adult rats showed the highest values at proestrus (p < 0.0001). The acute stress exposure induced a significant increase (p < 0.0001) of irCRF ovarian contents only at proestrus, without affecting irCRF at the other phases of the estrous cycle. Finally, no significant chan ges were found in ovarian irCRF after chronic intermittent stress. The proestrus-related changes of ovarian irCRF, confirming the adult ovar y as an extrahypothalamic source of CRF, may constitute a neuropeptide rgic signal involved in the gonadal reproductive cycle. Furthermore, t he stress-related changes of ovarian irCRF indicated that the gonad ma y be locally sensitive to acute stressful stimuli.