Studies on the site of origin and molecular form of the extrahypothalamic corticotrophin-releasing factor (CRF) in rats.

A homologous radioimmunoassay was developed for rat CRF. CRF immunoreactivity was found widely in the extrahypothalamic areas in the rat central nervous system in concentrations 1-3% of that in the median eminence. Large hypothalamic lesions including the paraventricular nucleus and the median eminence did not cause a decrease in the extrahypothalamic CRF concentrations. CRF of the rat hypothalamus and cerebral cortex both consisted of high and low molecular weight forms. In contrast the posterior pituitary and the spinal cord contained only low molecular weight forms. Upon gel filtration the low molecular weight CRF of the hypothalamus co-eluted with synthetic rat CRF whereas that of the spinal cord was considerably more retarded. The low molecular weight CRF of the posterior pituitary and cerebral cortex was slightly more retarded compared to synthetic rat CRF. We conclude that CRF in many extrahypothalamic brain areas and the spinal cord does not originate from the hypothalamus and that there is some heterogeneity in the molecular form of the extrahypothalamic CRF.