Low concentrations of ethanol do not affect radioligand binding to the delta-subunit-containing GABAA receptors in the rat brain

Brain Res. 2007 Aug 24;1165:15-20. doi: 10.1016/j.brainres.2007.06.051. Epub 2007 Jul 26.

Abstract

In the present study, we investigated the co-localization pattern of the delta subunit with other subunits of GABA(A) receptors in the rat brain using immunoprecipitation and Western blotting techniques. Furthermore, we investigated whether low concentrations of ethanol affect the delta-subunit-containing GABA(A) receptor assemblies in the rat brain using radioligand binding to the rat brain membrane homogenates as well as to the immunoprecipitated receptor assemblies. Our results revealed that delta subunit is not co-localized with gamma(2) subunit but it is associated with the alpha(1), alpha(4) or alpha(6), beta(2) and/or beta(3) subunit(s) of GABA(A) receptors in the rat brain. Ethanol (1-50 mM) neither affected [(3)H]muscimol (3 nM) binding nor diazepam-insensitive [(3)H]Ro 15-4513 (2 nM) binding in the rat cerebellum and cerebral cortex membranes. However, a higher concentration of ethanol (500 mM) inhibited the binding of these radioligands to the GABA(A) receptors partially in the rat cerebellum and cerebral cortex. Similarly, ethanol (up to 50 mM) did not affect [(3)H]muscimol (15 nM) binding to the immunoprecipitated delta-subunit-containing GABA(A) receptor assemblies in the rat cerebellum and hippocampus but it inhibited the binding partially at a higher concentration (500 mM). These results suggest that the native delta-subunit-containing GABA(A) receptors do not play a major role in the pharmacology of clinically relevant low concentrations of ethanol.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Affinity Labels / pharmacokinetics
  • Animals
  • Azides / pharmacokinetics
  • Benzodiazepines / pharmacokinetics
  • Binding, Competitive / drug effects
  • Brain / diagnostic imaging
  • Brain / drug effects*
  • Brain / metabolism
  • Central Nervous System Depressants / pharmacology*
  • Dose-Response Relationship, Drug
  • Ethanol / pharmacology*
  • Immunoprecipitation
  • Male
  • Muscimol / pharmacokinetics
  • Radioligand Assay
  • Radionuclide Imaging
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, GABA-A / metabolism*
  • Tritium / pharmacokinetics

Substances

  • Affinity Labels
  • Azides
  • Central Nervous System Depressants
  • Receptors, GABA-A
  • Tritium
  • Benzodiazepines
  • Muscimol
  • Ethanol
  • Ro 15-4513