• Jun-Wei Cao, Wuqiang Guan, Yong-Chun Yu, and Yinghui Fu.
• Jing'an District Center Hospital of Shanghai, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Fudan University, Shanghai, China.
• Neuroscience. 2020 Nov 21; 449: 147-156.

AbstractDendrite-targeting somatostatin-expressing interneurons (SST-INs) powerfully control signal integration and synaptic plasticity in pyramidal dendrites during cortical development. We previously showed that synaptic transmission from SST-INs to pyramidal cells (PCs) (SST-IN → PC) in the mouse visual cortex suddenly declined at around the second postnatal week. However, it is unclear what specific postsynaptic mechanisms underlie this developmental change. Using multiple whole-cell patch-clamp recordings, we found that application of an α5-GABAA receptor-selective inverse agonist, alpha5IA, significantly weakened SST-IN → PC unitary inhibitory postsynaptic currents (uIPSCs) in layer 2/3 of the mouse visual cortex, but had no effect on uIPSCs from SST-INs to other types of interneurons. The extent of alpha5IA-induced reduction of SST-IN → PC synaptic transmission was significantly larger at postnatal days 11-13 (P11-13) than P14-17. Moreover, α5-subunit-containing GABAA receptors (α5-GABAARs)-mediated uIPSCs had slow rise and decay kinetics. Apart from pharmacological test, we observed that SST-IN → PC synapses did indeed contain α5-GABAARs by immunogold labeling for electron microscopy. More importantly, coinciding with the weakening of SST-IN → PC synaptic transmission, the number of α5-GABAAR particles in SST-IN → PC synapses significantly decreased at around the second postnatal week. Together, these data indicate that α5-GABAARs are involved in synaptic transmission from SST-INs to PCs in the neocortex, and are significantly diminished around the second postnatal week.Copyright © 2020 IBRO. Published by Elsevier Ltd. All rights reserved.

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