Changes in corticotropin releasing factor (CRF) concentrations in the rat brain during pregnancy and postpartum

We have recently shown that brain and plasma concentrations of progesterone and its neuroactive derivatives allopregnanolone (AP) and allotetrahydrodeoxycorticosterone (THDOC) increased progressively during pregnancy, peaking between 15 and 19 day and returning to control (females in estrus) levels before delivery (21 day) (PNAS 95: 13284, 1998). Since CRF is thought to be the major physiological modulator of the hypothalamic-pituitary-adrenocortical (HPA) axis, in this study we evaluate putative changes in brain CRF concentrations during pregnancy and after delivery. CRF content in the cerebral cortex markedly increased on day 19 of pregnancy (53.4 ± 6.04 pg/ml prot) with respect to estrus female (10.5 ± 1.07 pg/ml prot), was still higher on day 21 (32.4 ± 7.1 pg/ml prot) and remained unchanged 2 days postpartum. CRF concentration also increased in the hippocampus, peaking between 15 and 19 day of pregnancy (?100 ± 13 pg/ml prot) and returning to estrus levels (50.3 ± 4.2 pg/ml prot) before delivery (21 day). CRF levels in the hippocampus remained unchanged in the postpartum period. In contrast, the CRF mRNA expression in the cerebral cortex and hippocampus decreased (?-30%) during pregnancy and after delivery. The time-dependent relationship between the marked alterations in brain CRF concentrations and the changes in neuroactive steroid levels during pregnancy and postpartum will be discussed.