Oxytocinergic neurons in rat hypothalamus. Dexamethasone-reversible increase in their corticotropin-releasing factor-41-like immunoreactivity in response to osmotic stimulation

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Abstract

Recent results have demonstrated altered corticotropin-releasing factor (CRF)-41 content of the neurointermediate lobe (NIL) of the pituitary gland in response to various manipulations including osmotic stimulation. This study was undertaken to determine whether changes in CRF-41 content of the NIL are accompanied by changes in intensity of CRF-41-like immunoreactivity (CRF-41-LI) of neurosecretory neurones of the hypothalamus in response to osmotic stimulation. Wistar rats of both sexes given either tap water ad libitum, 2% NaCl solution, or access to tap water was limited to 20 min daily, for 7 days. Subsets of rats from each group were adrenalectomized (ADX) or treated with dexamethasone (DEX). Thirty-six hour before perfusion with fixative consisting of buffered formaldehyde and picric acid, animals received 75 μg colchicine i.c.v. Forty micrometer thick vibratome sections were stained for CRF-LI, arginine vasopressin (AVP-LI) and oxytocin (OXY-LI) using the avidin-biotin-peroxidase complex method. In response to both types of osmotic stimulation magnocellular neurones of the paraventricular (PVN) and supraoptic nuclei (SON) showed increased CRF-LI, AVP-LI and OXY-LI, while CRF-LI of parvocellular perikarya of the PVN decreased. The enhanced CRF-LI seemed to appear in a subset of magnocellular neurones with OXY-LI but not AVP-LI. Increased staining intensities were also observed in magnocellular neurones in ADX rats challenged osmotically. In contrast, systemic DEX administration, as well as implantation of DEX in the area on the SON, sharply attenuated CRF-LI but not AVP-LI or OXY-LI of magnocellular neurones in osmotically stimulated rats. Our results demonstrate that osmotic stimulation causes increases in CRF-41-L1 in addition to AVP-LI and OXY-LI of magnocellular neurones, presumably due to the increased synthesis rate of these peptides. However, magnocellular synthesis of CRF-41 appears to be regulated differently from AVP and OXY since DEX seems to inhibit the increased synthesis rate of CRF-41 but not that of AVP or OXY in these cells in response to osmotic stimulation.

Original languageEnglish
Pages (from-to)515-522
Number of pages8
JournalNeuroendocrinology
Volume51
Issue number5
Publication statusPublished - Jan 1 1990

Keywords

  • CRF-41-like immunoreactivity
  • Dexamethasone
  • Magnocellular neurones
  • Osmotic stimulation

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Endocrinology
  • Endocrine and Autonomic Systems
  • Cellular and Molecular Neuroscience

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