Yamamoto T, Samejima A, Oka H
Department of Physiology, Fukui Medical School, Japan.
Exp Brain Res. 1990;80(1):12-22. doi: 10.1007/BF00228842.
A total of 141 pyramidal neurons in the cat primary somatosensory cortex (SI) were recorded intracellularly under Nembutal anesthesia (7 in layer II, 43 in layer III, 8 in layer IV, 58 in layer V and 25 in layer VI). Most neurons were identified by intracellular staining with HRP, though some layer V pyramidal neurons were identified only electrophysiologically with antidromic activation of medullary pyramid (PT) or pontine nuclear (PN) stimulation. Excitatory synaptic potentials (EPSPs) were analyzed with stimulation of the superficial radial nerve (SR), the ventral posterolateral nucleus (VPL) in the thalamus and the thalamic radiation (WM). The pyramidal neurons in layers III and IV received EPSPs at the shortest latency: 9.1 +/- 2.1 ms (Mean +/- S.D.) for SR and 1.6 +/- 0.7 ms for VPL stimulation. Layer II pyramidal neurons also responded at a short latency to VPL stimulation (1.7 +/- 0.5 ms), though their mean latencies for SR-induced EPSPs were relatively longer (10.6 +/- 1.9 ms). The mean latencies were much longer in layers V and VI pyramidal neurons (10.2 +/- 2.4 ms and 2.9 +/- 1.5 ms in layer V pyramidal neurons and 9.9 +/- 2.5 ms and 2.8 +/- 1.6 ms in layer VI pyramidal ones, respectively for SR and VPL stimulation). The comparison of the latencies between VPL and WM stimulation indicates that most layer III-IV pyramidal neurons and some pyramidal cells in layers II, V and VI received monosynaptic inputs from VPL. These findings are consistent with morphological data on the laminar distribution of thalamocortical fibers, i.e., thalamocortical fibers terminate mainly in the deeper part of layers III and IV with some collaterals in layers V, VI and II-I. The time-sequences of the latencies of VPL-EPSPs indicate that corticocortical and/or transcallosal neurons (pyramidal neurons in layers II and III) fire first and are followed by firing of the output neurons projecting to the subcortical structures (pyramidal neurons in layers V and VI).
在戊巴比妥麻醉下，对猫初级体感皮层（SI）中的141个锥体神经元进行了细胞内记录（II层7个，III层43个，IV层8个，V层58个，VI层25个）。大多数神经元通过辣根过氧化物酶（HRP）细胞内染色进行鉴定，不过一些V层锥体神经元仅通过延髓锥体（PT）的逆向激活或脑桥核（PN）刺激进行电生理鉴定。通过刺激桡浅神经（SR）、丘脑腹后外侧核（VPL）和丘脑辐射（WM）来分析兴奋性突触后电位（EPSP）。III层和IV层的锥体神经元接受EPSP的潜伏期最短：SR刺激时为9.1±2.1毫秒（平均值±标准差），VPL刺激时为1.6±0.7毫秒。II层锥体神经元对VPL刺激也有较短潜伏期的反应（1.7±0.5毫秒），不过它们由SR诱发的EPSP的平均潜伏期相对较长（10.6±1.9毫秒）。V层和VI层锥体神经元的平均潜伏期长得多（V层锥体神经元SR和VPL刺激时分别为10.2±2.4毫秒和2.9±1.5毫秒，VI层锥体神经元分别为9.9±2.5毫秒和2.8±1.6毫秒）。VPL和WM刺激潜伏期的比较表明，大多数III - IV层锥体神经元以及II、V和VI层中的一些锥体细胞接受来自VPL的单突触输入。这些发现与丘脑皮质纤维层状分布的形态学数据一致，即丘脑皮质纤维主要终止于III层和IV层的深部，在V层、VI层以及II - I层有一些侧支。VPL - EPSP潜伏期的时间序列表明，皮质 - 皮质和/或胼胝体间神经元（II层和III层的锥体神经元）首先放电，随后是投射到皮质下结构的输出神经元（V层和VI层的锥体神经元）放电。
