title: Mechanism of restoration of ACTH release in rats with long-term lesions of the paraventricular nuclei.
abstract: The effects of lesions in the paraventricular nucleus (PVN) on the adrenocortical response to ether stress were investigated in neurohypophysectomized and intact rats. During the first 4 days after placement of lesions in the PVN, the corticosterone response to ether stress was almost completely inhibited. It then gradually increased and, within 4-6 weeks of surgery, was restored to about 60% of that in sham-operated rats. Basal plasma concentrations of corticosterone were low in rats after placement of lesions in the PVN and/or after neurointermediate lobectomy (NILX). Corticosterone responses to ether stress were similar in groups submitted to PVN lesions and/or NILX, and lower than those in the appropriate sham-operated groups. In all lesioned groups, plasma ACTH concentrations after a combination of stressors (ether plus laparotomy) were also lower than those in the sham-operated groups. Six weeks after lesioning of the PVN, immunoreactive rat corticotrophin-releasing factor-41 (rCRF-41) concentrations in stalk-median eminence (SME) extract fell to about 5% of that in sham-operated rats, while immunoreactive arginine vasopressin (AVP) concentrations did not change. Immunohistochemistry revealed a substantial decrease in rCRF-41 immunostaining of the median eminence 6 weeks after lesioning of the PVN, though randomly located clusters of stained terminals were still seen in the whole rostro-caudal extent of the median eminence. A mixture containing synthetic rCRF-41 and AVP, in proportions similar to those in SME extracts from sham-operated rats, caused significantly less release of ACTH from anterior pituitary cell cultures than did SME extracts from sham-operated rats.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000302:Adrenal Cortex / Q000378:metabolism*; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism; D003345:Corticosterone / Q000378:metabolism; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism; D008297:Male; D010286:Paraventricular Hypothalamic Nucleus / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013312:Stress, Physiological / Q000503:physiopathology; D013997:Time Factors
chemical_list: D001127:Arginine Vasopressin; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D003345:Corticosterone