Action of zolpidem on responses to GABA in relation to mRNAs for GABA(A) receptor alpha subunits within single cells: Evidence for multiple functional GABA(A) isoreceptors on individual neurons

H. E. Criswell, T. J. McCown, S. S. Moy, G. S. Oxford, R. A. Mueller, A. L. Morrow, G. R. Breese

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The relationship between zolpidem sensitivity and GABA(A) receptor alpha subunits was studied in individual dissociated neurons from rat brain. Using whole-cell recording, similar EC50 values were demonstrated for the effect of γ-aminobutyric acid (GABA) on gated-chloride currents from substantia nigra reticulata (SNR) and lateral septal neurons. Subsequently, many neurons from both the SNR or lateral septum were found to exhibit enhanced GABA-gated chloride currents across concentrations of zolpidem ranging from 10 to 300 nM. Some neurons exhibited a greater than 20% increase in responsiveness to GABA at 30 nM of zolpidem without further increase at higher concentrations of zolpidem. Conversely, zolpidem enhancement of GABA from another group of neurons was not observed at 30 nM zolpidem, but between 100 and 300 nM the response to GABA increased greater than 20%, Finally, a third group of neurons reached both of these criteria for zolpidem enhancement of GABA. This latter spectrum of responses to GABA after varying concentrations of zolpidem was consistent with the presence of either two GABA(A) receptors or a single receptor with differing affinities for zolpidem on an individual neuron. Following determination of the sensitivity of neurons from SNR or lateral septum to zolpidem, cytoplasm was extracted from some individual cells to allow identification of cellular mRNAs for the α1, α2 and α3 GABA(A) receptor subunits with RT-PCR. Those neurons that responded to the 30 nM zolpidem concentration invariably expressed the α1-GABA(A) receptor subunit. This result is consistent with the GABA(A) α1-receptor subunit being an integral part of a functional high-affinity zolpidem type 1-BZD receptor complex on neurons in brain. Those neurons which showed enhancement of GABA from 100 to 300 nM zolpidem contained mRNAs for the α2 and/or the α3 receptor subunits, a finding consistent with these alpha subunits forming type 2-BZD receptors. Some individual dissociated SNR neurons were sensitive to both low and high concentrations of zolpidem and contained mRNAs for all three α-receptor subunits. These latter individual neurons are proposed to have at least two functional GABA(A) receptor subtypes. Thus, the present investigation emphasizes the importance of characterizing the relationship between endogenous GABA(A) receptor function and the presence of specific structural components forming GABA(A) receptor subtypes on neurons.

Original languageEnglish (US)
Pages (from-to)1641-1652
Number of pages12
Issue number11-12
StatePublished - Jan 1 1997



  • BZD receptor (type 1)
  • BZD receptor (type 2)
  • Benzodiazepine (BZD)
  • GABA(A) receptor subunits
  • Patch-clamp electrophysiology
  • Receptor subunit mRNAs
  • Single-cell RT-PCR
  • Zolpidem

ASJC Scopus subject areas

  • Pharmacology
  • Cellular and Molecular Neuroscience

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