Serwanski David R, Miralles Celia P, Christie Sean B, Mehta Ashok K, Li Xuejing, De Blas Angel L
Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut 06269, USA.
J Comp Neurol. 2006 Nov 20;499(3):458-70. doi: 10.1002/cne.21115.
The alpha5 subunit of the GABA(A) receptors (GABA(A)Rs) has a restricted expression in the brain. Maximum expression of this subunit occurs in the hippocampus, cerebral cortex, and olfactory bulb. Hippocampal pyramidal cells show high expression of alpha5 subunit-containing GABA(A)Rs (alpha5-GABA(A)Rs) both in culture and in the intact brain. A large pool of alpha5-GABA(A)Rs is extrasynaptic and it has been proposed to be involved in the tonic GABAergic inhibition of the hippocampus. Nevertheless, there are no studies on the localization of the alpha5-GABA(A)Rs at the electron microscope (EM) level. By using both immunofluorescence of cultured hippocampal pyramidal cells and EM postembedding immunogold of the intact hippocampus we show that, in addition to the extrasynaptic pool, there is a pool of alpha5-GABA(A)Rs that concentrates at the GABAergic synapses in dendrites of hippocampal pyramidal cells. The results suggest that the synaptic alpha5-GABA(A)Rs might play a role in the phasic GABAergic inhibition of pyramidal neurons in hippocampus and cerebral cortex.
γ-氨基丁酸A受体（GABA(A)Rs）的α5亚基在大脑中的表达受限。该亚基的最高表达出现在海马体、大脑皮层和嗅球。海马体锥体细胞在培养物和完整大脑中均显示出含α5亚基的GABA(A)Rs（α5-GABA(A)Rs）的高表达。大量的α5-GABA(A)Rs位于突触外，有人提出其参与海马体的紧张性GABA能抑制。然而，尚无关于α5-GABA(A)Rs在电子显微镜（EM）水平定位的研究。通过使用培养的海马体锥体细胞的免疫荧光和完整海马体的EM包埋后免疫金标法，我们发现，除了突触外池，还有一组α5-GABA(A)Rs聚集在海马体锥体细胞树突中的GABA能突触处。结果表明，突触α5-GABA(A)Rs可能在海马体和大脑皮层中锥体细胞的相位性GABA能抑制中发挥作用。
