PT - JOURNAL ARTICLE AU - Patrick S. Mangan AU - Chengsan Sun AU - Mackenzie Carpenter AU - Howard P. Goodkin AU - Werner Sieghart AU - Jaideep Kapur TI - Cultured Hippocampal Pyramidal Neurons Express Two Kinds of GABA<sub>A</sub> Receptors AID - 10.1124/mol.104.007385 DP - 2005 Mar 01 TA - Molecular Pharmacology PG - 775--788 VI - 67 IP - 3 4099 - http://molpharm.aspetjournals.org/content/67/3/775.short 4100 - http://molpharm.aspetjournals.org/content/67/3/775.full SO - Mol Pharmacol2005 Mar 01; 67 AB - We combined a study of the subcellular distribution of the α1, α2, α4, β1, β2/3, γ2, and δ 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 α1, α2, β2/3, and γ2 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, α4, β1, and δ 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 α1, α2, β2/3, and γ2 subunits were contained in clustered receptors. The second kind was distributed diffusely in the extrasynaptic membrane. The α4, β1, and δ 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 α4, β1, and δ subunits.