Modulation of arginine vasopressin secretion from cultured ovine hypothalamic cells by glucocorticoids and opioid peptides.
In sheep, arginine vasopressin (AVP) appears to be a more potent ACTH-releasing factor than ovine corticotrophin-releasing hormone. In order to investigate the neuroendocrine regulation of AVP secretion we have developed a novel system for maintaining fetal ovine hypothalamic neurones in serum-free culture. Hypothalamic neurones derived from fetal sheep at day 70 gestation (term = 145 days) secreted AVP under basal conditions and in response to repeated potassium-induced depolarizations, for up to 35 days in vitro. AVP secretion was time- and calcium-dependent. AVP secreted from ovine hypothalamic cells co-eluted with synthetic AVP on a Sephadex chromatography column and diluted in parallel with AVP standard in the radioimmunoassay. The addition of cortisol (150 nM) to medium bathing ovine hypothalamic cells significantly inhibited basal, and potassium-induced AVP secretion without altering the AVP content of the cell cultures. Furthermore, the opioid peptide [D-Pro10]Dynorphin(1-11) which acts via the kappa opioid receptor, significantly inhibited basal and potassium-stimulated AVP secretion, an effect which was abolished when cells were cultured in the presence of cortisol. These data show that hypothalamic AVP is a site for negative feedback regulation within the ovine hypothalamic-pituitary-adrenal axis. Furthermore, these data suggest that the kappa opioid system inhibits AVP secretion from ovine hypothalamic neurones, a response which is modulated by glucocorticoids.
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MRC Reproductive Biology Unit, Centre for Reproductive Biology, Edinburgh, UK.
Gillies
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G
Brooks
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D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism*; D002478:Cells, Cultured; D004399:Dynorphins / Q000494:pharmacology; D005938:Glucocorticoids / Q000494:pharmacology*; D007031:Hypothalamus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018847:Opioid Peptides / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011863:Radioimmunoassay; D012756:Sheep
D005938:Glucocorticoids; D018847:Opioid Peptides; D010446:Peptide Fragments; D001127:Arginine Vasopressin; D004399:Dynorphins; C044620:dynorphin (1-11); D011188:Potassium