Scheppach Christian
Physiological Laboratory, Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
Institute of Physics, University of Freiburg, Freiburg, Germany.
Physiol Rep. 2016 Dec;4(24). doi: 10.14814/phy2.13051.
N-Methyl-D-aspartate (NMDA) receptors are ion channels activated by the neurotransmitter glutamate in the mammalian brain and are important in synaptic function and plasticity, but are also found in extrasynaptic locations and influence neuronal excitability. There are different NMDA receptor subtypes which differ in their single-channel conductance. Recently, synaptic plasticity has been studied in the mouse barrel cortex, the primary sensory cortex for input from the animal's whiskers. Pharmacological data imply the presence of low-conductance NMDA receptors in spiny stellate neurons of cortical layer 4, but of high-conductance NMDA receptors in pyramidal neurons of layer 2/3. Here, to obtain complementary electrophysiological information on the functional NMDA receptors expressed in layer 4 and layer 2/3 neurons, single NMDA receptor currents were recorded with the patch-clamp method. Both cell types were found to contain high-conductance as well as low-conductance NMDA receptors. The results are consistent with the reported pharmacological data on synaptic plasticity, and with previous claims of a prominent role of low-conductance NMDA receptors in layer 4 spiny stellate neurons, including broad integration, amplification and distribution of excitation within the barrel in response to whisker stimulation, as well as modulation of excitability by ambient glutamate. However, layer 4 cells also expressed high-conductance NMDA receptors. The presence of low-conductance NMDA receptors in layer 2/3 pyramidal neurons suggests that some of these functions may be shared with layer 4 spiny stellate neurons.
N-甲基-D-天冬氨酸（NMDA）受体是哺乳动物大脑中由神经递质谷氨酸激活的离子通道，在突触功能和可塑性方面发挥重要作用，但也存在于突触外位置并影响神经元兴奋性。存在不同的NMDA受体亚型，它们的单通道电导有所不同。最近，在小鼠桶状皮质（即接收动物胡须输入的主要感觉皮质）中对突触可塑性进行了研究。药理学数据表明，皮质第4层的棘状星形神经元中存在低电导NMDA受体，而第2/3层的锥体神经元中存在高电导NMDA受体。在此，为了获取关于第4层和第2/3层神经元中表达的功能性NMDA受体的补充电生理信息，采用膜片钳方法记录单个NMDA受体电流。发现这两种细胞类型均含有高电导和低电导NMDA受体。这些结果与报道的关于突触可塑性的药理学数据一致，也与之前关于低电导NMDA受体在第4层棘状星形神经元中发挥重要作用的说法一致，这些作用包括对胡须刺激的广泛整合、兴奋在桶内的放大和分布，以及环境谷氨酸对兴奋性的调节。然而，第4层细胞也表达高电导NMDA受体。第2/3层锥体神经元中存在低电导NMDA受体表明，其中一些功能可能与第4层棘状星形神经元共有。
