The α4 subunit of the GABA(A) receptors from rat brain and retina

Z. U. Khan, A. Gutiérrez, A. K. Mehta, C. P. Miralles, A. L. De Blas

Research output: Contribution to journalArticlepeer-review

38 Scopus citations

Abstract

A novel anti-α4 antibody has been used for the purification and characterization of the α4-containing GABA(A) receptors in the rat brain and for studying the immunocytochemical distribution of the α4 subunit peptide in rat brain and retina. The anti-α4 antibody recognized a 66 kDa peptide in brain membranes and immunoprecipitated 10-28% of the brain GABA(A) receptors in various brain regions as determined by [3H]muscimol binding. The highest immunoprecipitation values were obtained in the thalamus and the lowest in the cerebellum. Surprisingly, the receptors immunoprecipitated by anti-α4 showed little or no diazepam-insensitive or diazepam-sensitive [3H]Ro15-4513 binding sites in any brain region. In the cerebellum, where 25% of the [3H]Ro15-4513 binding is diazepam-insensitive, much of the latter was immunoprecipitated by an anti-α6 antibody but not by the anti-α4 antibody. Immunoblots of immunoaffinity-purified GABA(A) receptors from the cerebral cortex on immobilized anti-α4 revealed molecular colocalization of α4 and γ2. However, the absence of significant benzodiazepine binding in these GABA(A) receptors suggests that the assembly of the α4 and γ2 subunits in the cerebral cortex and in other brain regions is such that they do not normally form diazepam-insensitive [3H]Ro15-4513 binding sites. This result contrasts with the presence of diazepam-insensitive [3H]Ro15-4513 binding sites in the GABA(A) receptors expressed in heterologous systems resulting from the combination of α4, γ2 and β2 subunits. Immunocytochemistry has revealed the abundance of α4 peptide immunoreactivity in the thalamus and dentate gyrus (mainly in the hilar neurons and the inner third of the granule cell layer). The α4 immunoreactivity is also present in the external plexiform layer of the olfactory bulb and in all layers of the neocortex and pyriform cortex. In the retina, α4 is concentrated on ganglion cells (including some giant ganglion cells), the inner plexiform layer and to a lesser extent in the outer plexiform layer.

Original languageEnglish (US)
Pages (from-to)1315-1322
Number of pages8
JournalNeuropharmacology
Volume35
Issue number9-10
DOIs
StatePublished - 1996
Externally publishedYes

Keywords

  • Antibody
  • Benzodiazepine receptor
  • GABA(A) receptor
  • Immunocytochemistry

ASJC Scopus subject areas

  • Pharmacology
  • Cellular and Molecular Neuroscience

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