Corticoliberin (CRF) activity in selected hypothalamic regions in rats with anterolateral hypothalamic cuts

Abstract The hypothalamic path of the corticoliberin (CRF) containing fibers was investigated in male rats with an anterolateral cut around the medial basal hypothalamus (MBH). Frozen samples of different brain regions were taken from cryostat sections and they were extracted and bioassayed using immunoreactive ACTH release from cell cultures of anterior pituitary as an index of CRF activity. Three days after placing an anterolateral cut there was no change in CRF activity of tissue surrounding a thalamic cut, but a significant rise was observed in the strip of tissue surrounding the hypothalamic cut at the level of the retrochiasmatic area. Seven days after the operation CRF activity decreased in the samples of the stalk-median eminence as well as the arcuate nucleus but it was maintained in the samples taken from that portion of the lateral retrochiasmatic area, which was outside the hypothalamic cut. We suggest that CRF containing fibers traverse the basallateral part of the retrochiasmatic area and the arcuate-ventro-medial region of the MBH en route to the stalk-median eminence and neural lobe. Within 3 days following partial isolation of the MBH neurosecretory material including CRF accumulates near the hypothalamic cut by redistribution in the damaged neurons, while by 7 days after transection the distal part of the axons in the MBH degenerates and is removed.