These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Activation of A-type gamma-aminobutyric acid receptors excites gonadotropin-releasing hormone neurons.
    Author: DeFazio RA, Heger S, Ojeda SR, Moenter SM.
    Journal: Mol Endocrinol; 2002 Dec; 16(12):2872-91. PubMed ID: 12456806.
    Abstract:
    Gamma-aminobutyric acid (GABA), acting through GABA(A) receptors (GABA(A)R), is hypothesized to suppress reproduction by inhibiting GnRH secretion, but GABA actions directly on GnRH neurons are not well established. In green fluorescent protein-identified adult mouse GnRH neurons in brain slices, gramicidin-perforated-patch-clamp experiments revealed the reversal potential (E(GABA)) for current through GABA(A)Rs was depolarized relative to the resting potential. Furthermore, rapid GABA application elicited action potentials in GnRH neurons but not controls. The consequence of GABA(A)R activation depends on intracellular chloride levels, which are maintained by homeostatic mechanisms. Membrane proteins that typically extrude chloride (KCC-2 cotransporter, CLC-2 channel) were absent from the GT1-7 immortalized GnRH cell line and GnRH neurons in situ or were not localized to the proper cell compartment for function. In contrast, GT1-7 cells and some GnRH neurons expressed the chloride-accumulating cotransporter, NKCC-1. Patch-clamp experiments showed that blockade of NKCC hyperpolarized E(GABA) by lowering intracellular chloride. Regardless of reproductive state, rapid GABA application excited GnRH neurons. In contrast, bath application of the GABA(A)R agonist muscimol transiently increased then suppressed firing; suppression persisted 4-15 min. Rapid activation of GABA(A)R thus excites GnRH neurons whereas prolonged activation reduces excitability, suggesting the physiological consequence of synaptic activation of GABA(A)R in GnRH neurons is excitation.
    [Abstract] [Full Text] [Related] [New Search]