Differential synaptic localization of two major γ-aminobutyric acid type A receptor α subunits on hippocampal pyramidal cells

Abstract

Hippocampal pyramidal cells, receiving domain specific GABAergic inputs, express up to 10 different subunits of the γ-aminobutyric acid type A (GABA(A)) receptor, but only 3 different subunits are needed to form a functional pentameric channel. We have tested the hypothesis that some subunits are selectively located at subsets of GABAergic synapses. The α1 subunit has been found in most GABAergic synapses on all postsynaptic domains of pyramidal cells. In contrast, the α2 subunit was located only in a subset of synapses on the somata and dendrites, but in most synapses on axon initial segments innervated by axo-axonic cells. The results demonstrate that molecular specialization in the composition of postsynaptic GABA(A) receptor subunits parallels GABAergic cell specialization in targeting synapses to a specific domain of postsynaptic cortical neurons.