Dendrite-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-GABA_A 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 GABA_A receptors (α5-GABA_ARs)-mediated uIPSCs had slow rise and decay kinetics. Apart from pharmacological test, we observed that SST-IN → PC synapses did indeed contain α5-GABA_ARs by immunogold labeling for electron microscopy. More importantly, coinciding with the weakening of SST-IN → PC synaptic transmission, the number of α5-GABA_AR particles in SST-IN → PC synapses significantly decreased at around the second postnatal week. Together, these data indicate that α5-GABA_ARs are involved in synaptic transmission from SST-INs to PCs in the neocortex, and are significantly diminished around the second postnatal week.

靶向树突的生长抑素表达中间神经元（SST-INs）可以有效控制皮质发育过程中锥体突突中的信号整合和突触可塑性。我们先前显示，小鼠视皮层中从SST-IN到锥体细胞（PC）（SST-IN→PC）的突触传递在出生后第二周左右突然下降。但是，目前尚不清楚什么特定的突触后机制是这种发育变化的基础。使用多个全细胞膜片钳记录，我们发现α5-GABAA_的应用受体选择性反向激动剂alpha5IA显着减弱了小鼠视皮质2/3层中的SST-IN→PC单一抑制性突触后电流（uIPSC），但对从SST-IN到其他类型的中间神经元的uIPSC没有影响。出生后11-13天（P11-13），α5IA诱导的SST-IN→PC突触传递减少的程度明显大于P14-17。此外，含有α5亚单位-GABA_甲受体（α5-GABA_甲RS） -介导的uIPSCs有缓慢的上升和衰减动力学。除了药理试验中，我们观察到，SST-IN→PC突触确实含有α5-GABA_一个通过电子显微镜免疫标记卢比。更重要的是，与SST-IN→PC突触传递的减弱相一致，α5-GABA的数量_甲在SST-IN→PCř颗粒在围绕第二产后周突触显著降低。总之，这些数据表明，α5-GABA_一个卢比涉及从SST-INS突触传递到大脑皮层电脑，并围绕第二产后一周都显著减少。