Magnesium Potentiation of the Function of Native and Recombinant GABA(A) Receptors

Neuroreport. 2001 Jul 20;12(10):2175-9. doi: 10.1097/00001756-200107200-00026.

Abstract

Mg2+ decreased basal and GABA-inhibited t-butylbicyclophosphoro[35S]thionate binding to GABAA receptor ion channels in rat brain sections up to 1 mM, but increased the binding at 10 mM. The Mg2+-effect was detectable in the presence of a specific GABA site competitive antagonist. Two-electrode voltage clamp recordings of recombinant alpha1beta2gamma2S, alpha1beta2, alpha2beta2gamma2S and alpha2beta2 GABAA receptors revealed a potentiation by 0.1-1 mM Mg2+ of EC20 GABA-evoked ion currents. At 10 mM, Mg2+ decreased the currents. In the absence of GABA, Mg2+ did not evoke any currents. The results show that physiologically relevant Mg2+ concentrations affect the GABA responses on GABAA receptors in native and the main recombinant receptor subtypes, suggesting putative Mg2+ binding sites on the receptor complex.

MeSH terms

  • Action Potentials / drug effects*
  • Action Potentials / physiology
  • Animals
  • Autoradiography
  • Binding Sites / drug effects
  • Brain / drug effects*
  • Brain / metabolism
  • Bridged Bicyclo Compounds, Heterocyclic / metabolism
  • Convulsants / metabolism
  • Dose-Response Relationship, Drug
  • Drug Synergism
  • Electrophysiology
  • Magnesium Chloride / pharmacology*
  • Male
  • Oocytes / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, GABA-A / metabolism
  • Receptors, GABA-A / physiology*
  • Recombinant Proteins / pharmacology
  • Xenopus laevis
  • gamma-Aminobutyric Acid / pharmacology

Substances

  • Bridged Bicyclo Compounds, Heterocyclic
  • Convulsants
  • Receptors, GABA-A
  • Recombinant Proteins
  • Magnesium Chloride
  • gamma-Aminobutyric Acid
  • tert-butylbicyclophosphorothionate