title: Cultured Hippocampal Pyramidal Neurons Express Two Kinds of GABAA Receptors.
abstract: We combined a study of the subcellular distribution of the alpha1, alpha2, alpha4, beta1, beta2/3, gamma2, and delta subunits of the GABAA receptor with an electrophysiological analysis of GABAA receptor currents determine the to types of receptors expressed on cultured hippocampal pyramidal neurons. The immunocytochemistry study demonstrated that alpha1, alpha2, beta2/3, and gamma2 subunits formed distinct clusters of various sizes, which were colocalized with clusters of glutamate decarboxylase (GAD) immunoreactivity at rates ranging from 22 to 58%. In contrast, alpha4, beta1, and delta subunits were distributed diffusely over the cell soma and neuronal processes of cultured neurons and did not colocalize with the synaptic marker GAD. Whole-cell GABA receptor currents were moderately sensitive to GABAA and were modulated by diazepam. The whole-cell currents were also enhanced by the neurosteroid allopregnanolone (10 nM). Tonic currents, measured as changes in baseline current and noise, were sensitive to Zn2+, furosemide, and loreclezole; they were insensitive to diazepam. These studies suggest that two kinds of GABAA receptors are expressed on cultured hippocampal neurons. One kind of receptor formed clusters, which were present at GABAergic synapses and in the extrasynaptic membrane. The alpha1, alpha2, beta2/3, and gamma2 subunits were contained in clustered receptors. The second kind was distributed diffusely in the extrasynaptic membrane. The alpha4, beta1, and delta subunits were contained in these diffusely distributed receptors. The properties of tonic currents recorded from these neurons were similar to those from recombinant receptors containing alpha4, beta1, and delta subunits.
authors.affiliation: Department of Neurology, Box 800394, University of Virginia-HSC, Charlottesville, VA, USA.
authors.forename: Patrick S
authors.initials: PS
authors.lastname: Mangan
authors.forename: Chengsan
authors.initials: C
authors.lastname: Sun
authors.forename: Mackenzie
authors.initials: M
authors.lastname: Carpenter
authors.forename: Howard P
authors.initials: HP
authors.lastname: Goodkin
authors.forename: Werner
authors.initials: W
authors.lastname: Sieghart
authors.forename: Jaideep
authors.initials: J
authors.lastname: Kapur
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002712:Chlorides / Q000494:pharmacology; D003975:Diazepam / Q000494:pharmacology; D005968:Glutamate Decarboxylase / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008856:Microscopy, Fluorescence; D018408:Patch-Clamp Techniques; D021122:Protein Subunits / Q000235:genetics; D017966:Pyramidal Cells / Q000166:cytology / Q000502:physiology*; D051381:Rats; D011963:Receptors, GABA-A / Q000235:genetics*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D017967:Zinc Compounds / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
chemical_list: D002712:Chlorides; D021122:Protein Subunits; D011963:Receptors, GABA-A; D017967:Zinc Compounds; D005680:gamma-Aminobutyric Acid; C016837:zinc chloride; D005968:Glutamate Decarboxylase; D003975:Diazepam