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Electrophysiological recordings from gonadotrophs evidence for calcium channels mediated by gonadotropin releasing hormone

, : Electrophysiological recordings from gonadotrophs evidence for calcium channels mediated by gonadotropin releasing hormone. Neuroendocrinology 41(3): 258-268

The electrophysiological properties of gonadotrophs were studied in vitro, using the ovine adenohypophyseal pars tuberalis as a naturally enriched source of this cell type. Trypsin-dispersed pars tuberalis cells maintained in primary tissue culture had a membrane potential of -72 .+-. 4 mV (mean .+-. SEM) and an input resistance of 314 .+-. 38 M.OMEGA. Spontaneous action potentials were not observed; however, a single spike could be induced by depolarizing current injection. The hypophysiotrophic peptide gonadotrophin-releasing hormone (GnRH) increased membrane voltage fluctuations, but these fluctuations (.+-. 5-10 mV) did not induce action potentials or changes in membrane potential or resistance. Power spectra obtained from analysis of this noise indicated that the fundamental event underlying GnRH action has a mean life-time of 38.4 .+-. 4.5 ms. Cells incubated in recording medium secreted luteinizing hormone in response to GnRH and a GnRH-induced increase in voltage noise was inhibited by Ca2+ channnel antagonists. Gonadotrophin secretion is initiated by GnRH-induced Ca2+ channel activation and action potentials are not a prerequisite for gonadotrophin release.

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