Immunocytochemical localization of the α1 and β2/3 subunits of the GABA(A) receptor in relation to specific GABAergic synapses in the dentate gyrus

Z. Nusser, J. D B Roberts, A. Baude, J. G. Richards, W. Sieghart, P. Somogyi

Research output: Contribution to journalArticle

137 Citations (Scopus)

Abstract

Dentate granule cells receive spatially segregated GABAergic innervation from at least five types of local circuit neurons, and express mRNA for at least 11 subunits of the GABA(A) receptor. At most two to four different subunits are required to make a functional pentamer, raising the possibility that cells have on their surface several types of GABA(A) receptor channel, which may not be uniformly distributed. In order to establish the subcellular location of GABA(A) receptors on different parts of dentate neurons, the distribution of immunoreactivity for the α1 and β2/3 subunits of the receptor was studied using high-resolution immunocytochemistry. Light microscopic immunoperoxidase reactions revealed strong GABA(A) receptor immunoreactivity in the molecular layer of the dentate gyrus. Pre-embedding immunogold localization of the α1 and β2/3 subunits consistently showed extrasynaptic location of the GABA(A) receptor on the somatic, dendritic and axon initial segment membrane of granule cells, but failed to show receptors in synaptic junctions. Using a postembedding immunogold technique on freeze-substituted, Lowicryl-embedded tissue, synaptic enrichment of immunoreactivity for these subunits was found on both granule and non-principal cells. Only the postembedding immunogold method is suitable for revealing relative differences in receptor density at the subcellular level, giving ~20 nm resolution. The immunolabelling for GABA(A) receptor occupied the whole width of synaptic junctions, with a sharp decrease in labelling at the edge of the synaptic membrane specialization. Both subunits have been localized in the synaptic junctions between basket cell terminals and somata, and between axo-axonic cell terminals and axon initial segments of granule cells, with no qualitative difference in labelling. Receptor-immunopositive synapses were found at all depths of the molecular layer. Some of the boutons forming these dendritic synapses have been shown to contain GABA, providing evidence that some of the GABAergic cells that terminate only on the dendrites of granule cells also act through GABA(A) receptors. Double immunolabeliing experiments demonstrated that a population of GABA-immunopositive neurons expresses a higher density of immunoreactive GABA(A) receptor on their surface than principal cells. Interneurons were found to receive GABA(A) receptor-positive synapses on their dendrites in the hilus, molecular and granule cell layers. Receptor-immunopositive synapses were also present throughout the hilus on presumed messy cells. The results demonstrate that both granule cells and interneurons exhibit a compartmentalized distribution of the GABA(A) receptor on their surface, the postjunctional membrane to GABAergic terminals having the highest concentration of receptor. The α1 and β2/3 subunits have a similar distribution in synapses on the axon initial segment, soma, proximal and distal dendrites of granule cells. The very strong immunoreactivity of a subpopulation of GABAergic interneurons for GABA(A) receptors containing the α1 and β2/3 subunits predicts their high sensitivity to GABA and modulators of the receptor complex.

Original languageEnglish
Pages (from-to)630-646
Number of pages17
JournalEuropean Journal of Neuroscience
Volume7
Issue number4
Publication statusPublished - 1995

Fingerprint

Dentate Gyrus
GABA-A Receptors
Synapses
Interneurons
Dendrites
Carisoprodol
GABA Modulators
Immunohistochemistry
Neurons
GABAergic Neurons
Synaptic Membranes
Neurotransmitter Receptor
GABA Receptors
gamma-Aminobutyric Acid
Cell Membrane

Keywords

  • Benzodiazepine receptor
  • Cat
  • Disinhibition
  • Hippocampus
  • Inhibition
  • Rat
  • Synapse

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Immunocytochemical localization of the α1 and β2/3 subunits of the GABA(A) receptor in relation to specific GABAergic synapses in the dentate gyrus. / Nusser, Z.; Roberts, J. D B; Baude, A.; Richards, J. G.; Sieghart, W.; Somogyi, P.

In: European Journal of Neuroscience, Vol. 7, No. 4, 1995, p. 630-646.

Research output: Contribution to journalArticle

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AU - Somogyi, P.

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