GABA(A) receptors containing the alpha4-subunit: prevalence, distribution, pharmacology, and subunit architecture in situ

J Neurochem. 1997 Aug;69(2):806-14. doi: 10.1046/j.1471-4159.1997.69020806.x.


Recombinant GABA(A) receptors, expressed from alpha-, beta-, and gamma2-subunits, are diazepam-insensitive when the alpha-subunit is either alpha4 or alpha6. In situ, diazepam-insensitive receptors containing the alpha6-subunit are almost exclusively expressed in the granule cell layer of the cerebellum. However, diazepam-insensitive receptors are also expressed in forebrain areas. Here, we report on the presence of diazepam-insensitive GABA(A) receptors in various brain areas containing the alpha4-subunit. GABA(A) receptors immunoprecipitated with a newly developed alpha4-subunit-specific antiserum displayed a drug binding profile that was indistinguishable from those of alpha4beta2gamma2-recombinant receptors and diazepam-insensitive [3H]Ro 15-4513 binding sites in rat brain membranes. In addition, alpha4-subunit containing receptors and forebrain diazepam-insensitive receptors are present at comparably low abundance in rat brain and exhibit virtually identical patterns of distribution. Analysis of the subunit architecture of alpha4-subunit containing receptors revealed that the alpha4-subunit contributes to several receptor subtypes. Depending on the brain region, the alpha4-subunit can be coassembled with a second type of alpha-subunit variant being alpha1, alpha2, or alpha3. The data demonstrate that native receptors containing the alpha4-subunit are structurally heterogeneous, expressed at very low abundance in the brain, and display the drug binding profile of diazepam-insensitive [3H]Ro 15-4513 binding sites. Pharmacologically, these receptors may contribute to the actions of nonclassical ligands such as Ro 15-4513 and bretazenil.

MeSH terms

  • Animals
  • Azides / metabolism
  • Benzodiazepines / metabolism
  • Benzodiazepinones / metabolism
  • Brain / metabolism
  • Cell Membrane / metabolism
  • Cerebellum / chemistry
  • Diazepam / pharmacology
  • Flumazenil / metabolism
  • Immunohistochemistry
  • Immunosorbent Techniques
  • Macromolecular Substances
  • Male
  • Muscimol / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, GABA-A / analysis*
  • Receptors, GABA-A / chemistry*
  • Receptors, GABA-A / metabolism
  • Recombinant Proteins / metabolism


  • Azides
  • Benzodiazepinones
  • Macromolecular Substances
  • Receptors, GABA-A
  • Recombinant Proteins
  • Benzodiazepines
  • Muscimol
  • Flumazenil
  • Ro 15-4513
  • bretazenil
  • Diazepam