Corticotrophin-releasing factor immunoreactivity in the hypothalamus of the rat during the perinatal period.

Corticotrophin-releasing factor-41 (CRF-41) immunoreactivity has been measured in hypothalamic extracts of fetal (on days 17, 19 and 21 of gestation), neonatal (1, 2, 3 and 4 weeks of age) and adult rats with a specific radioimmunoassay developed for synthetic rat CRF-41. The hypothalamic content (fmol) and concentration (fmol/mg protein) of immunoreactive CRF-41 gradually increased with age. Chromatography of hypothalamic extracts on Sephadex G-50 Fine showed one single peak of immunoreactive CRF-41 which co-eluted with synthetic rat CRF-41. The retention time of hypothalamic CRF-41 during high-performance liquid chromatography was identical to that of synthetic rat CRF-41 at all stages investigated. These results are consistent with the development of neurones containing CRF-41-like molecules in both the hypothalamus and the median eminence of the fetus, as well as with the hypothalamic control of the cortico-stimulating function of the pituitary gland as early as day 19 of gestation.