Department of Neuroscience, Physiology, and Pharmacology, University College London, 21 University Street, London WC1E 6DE, UK.
Neuron. 2012 Aug 9;75(3):451-66. doi: 10.1016/j.neuron.2012.06.017.
Traditionally, NMDA receptors are located postsynaptically; yet, putatively presynaptic NMDA receptors (preNMDARs) have been reported. Although implicated in controlling synaptic plasticity, their function is not well understood and their expression patterns are debated. We demonstrate that, in layer 5 of developing mouse visual cortex, preNMDARs specifically control synaptic transmission at pyramidal cell inputs to other pyramidal cells and to Martinotti cells, while leaving those to basket cells unaffected. We also reveal a type of interneuron that mediates ascending inhibition. In agreement with synapse-specific expression, we find preNMDAR-mediated calcium signals in a subset of pyramidal cell terminals. A tuned network model predicts that preNMDARs specifically reroute information flow in local circuits during high-frequency firing, in particular by impacting frequency-dependent disynaptic inhibition mediated by Martinotti cells, a finding that we experimentally verify. We conclude that postsynaptic cell type determines presynaptic terminal molecular identity and that preNMDARs govern information processing in neocortical columns.
传统上,NMDA 受体位于突触后;然而,已经报道了假定的突触前 NMDA 受体(preNMDAR)。尽管它们被认为在控制突触可塑性方面发挥作用,但它们的功能尚未得到很好的理解,其表达模式也存在争议。我们证明,在发育中的小鼠视觉皮层的第 5 层中,preNMDAR 特异性控制来自其他锥体神经元和 Martinotti 细胞的输入到锥体神经元的突触传递,而对 basket 细胞的突触传递没有影响。我们还揭示了一种介导上行抑制的中间神经元类型。与突触特异性表达一致,我们在一小部分锥体神经元末梢中发现了 preNMDAR 介导的钙信号。一个调谐网络模型预测,preNMDAR 可在高频放电期间特异性地重新路由局部回路中的信息流,特别是通过影响由 Martinotti 细胞介导的频率依赖性双突触抑制,我们通过实验验证了这一发现。我们得出结论,突触后细胞类型决定了突触前末梢的分子特征,并且 preNMDAR 控制着新皮层柱中的信息处理。