Gonadotropin-releasing hormone neurons express KATP channels that are regulated by estrogen and responsive to glucose and metabolic inhibition

Chunguang Zhang, Martha A. Bosch, Jon E. Levine, Oline K. Rønnekleiv, Martin J. Kelly

Research output: Contribution to journalArticle

86 Scopus citations

Abstract

Gonadotropin-releasing hormone (GnRH) is released in a pulsatile manner that is dependent on circulating 17β-estradiol (E2) and glucose concentrations. However, the intrinsic conductances responsible for the episodic firing pattern underlying pulsatile release and the effects of E2 and glucose on these conductances are primarily unknown. Whole-cell recordings from mouse enhanced green fluorescent protein-GnRH neurons revealed that the K ATP channel opener diazoxide induced an outward current that was antagonized by the sulfonylurea receptor 1 (SUR1) channel blocker tolbutamide. Single-cell reverse transcription (RT)-PCR revealed that the majority of GnRH neurons expressed Kir6.2 and SUR1 subunits, which correlated with the diazoxide/tolbutamide sensitivity. Also, a subpopulation of GnRH neurons expressed glucokinase mRNA, a marker for glucose sensitivity. Indeed, GnRH neurons decreased their firing in response to low glucose concentrations and metabolic inhibition. The maximum diazoxide-induced current was approximately twofold greater in E2-treated compared with oil-treated ovariectomized females. In current clamp, estrogen enhanced the diazoxide-induced hyperpolarization to a similar degree. However, based on quantitative RT-PCR, estrogen did not increase the expression of Kir6.2 or SUR1 transcripts in GnRH neurons. In the presence of ionotropic glutamate and GABAA receptor antagonists, tolbutamide depolarized and significantly increased the firing rate of GnRH neurons to a greater extent in E2-treated females. Finally, tolbutamide significantly increased GnRH secretion from the preoptic-mediobasal hypothalamus. Therefore, it appears that KATP channels and glucokinase are expressed in GnRH neurons, which renders them directly responsive to glucose. In addition, KATP channels are involved in modulating the excitability of GnRH neurons in an estrogen-sensitive manner that ultimately regulates peptide release.

Original languageEnglish (US)
Pages (from-to)10153-10164
Number of pages12
JournalJournal of Neuroscience
Volume27
Issue number38
DOIs
StatePublished - Sep 19 2007

Keywords

  • Diazoxide
  • Glucokinase
  • Glucose responsive
  • GnRH secretion
  • Kir6.2
  • Metabolic stress
  • SUR1
  • Tolbutamide

ASJC Scopus subject areas

  • Neuroscience(all)

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