Luhmann H J, Reiprich R A, Hanganu I, Kilb W
Institute of Neurophysiology, University of Düsseldorf, Düsseldorf, Germany.
J Neurosci Res. 2000 Nov 15;62(4):574-84. doi: 10.1002/1097-4547(20001115)62:4<574::AID-JNR12>3.0.CO;2-0.
The cellular physiology of the primary somatosensory cortex was studied in postnatal day (P) 0 to P5 rats using whole-cell patch-clamp recordings. Visually identified Cajal-Retzius, subplate, bifurcated pyramidal, and immature, putatively migrating neurons showed resting membrane potentials between -44 and -50 mV and TTX-sensitive action potentials. Immature pyramidal neurons with the smallest surface area ( approximately 1,600 microm(2)) revealed the largest input resistance ( approximately 1.8 GOmega), and subplate cells with the largest surface area ( approximately 6,200 microm(2)) showed an input resistance of approximately 1 GOmega. Ontogenetically older Cajal-Retzius and subplate cells revealed shorter and larger action potentials compared to bifurcated and immature pyramidal neurons. Whereas Cajal-Retzius and subplate cells responded to injection of depolarizing current pulses with a repetitive nonadapting and fast spiking firing pattern, immature pyramidal neurons showed strong adaptation. Subplate cells revealed the fastest action potentials, largest sodium current amplitude (-714 pA), and highest sodium current density (-38 microA/cm(2)), enabling these cells to transmit afferent activity faithfully to postsynaptic neurons. Whereas all cell types expressed a high-voltage-activated (HVA) calcium current, none of them showed a significant low-voltage-activated calcium current. The largest peak (-25.5 microA/cm(2)) and steady-state (-7.6 microA/cm(2)) HVA calcium current density could be observed in immature presumed migrating neurons. In contrast, Cajal-Retzius and subplate neurons showed a significantly lower peak (-4.9 microA/cm(2)) and steady-state (<-3.3 microA/cm(2)) HVA calcium current density. Whereas a large HVA calcium current may promote neuronal migration of immature neurons, low intracellular calcium levels may provoke apoptosis in Cajal-Retzius and subplate cells.
采用全细胞膜片钳记录技术，对出生后第0天（P0）至第5天（P5）大鼠的初级体感皮层细胞生理学进行了研究。通过视觉识别的 Cajal-Retzius 细胞、板下层细胞、分叉锥体神经元以及不成熟的、推测正在迁移的神经元，其静息膜电位在-44至-50 mV之间，且动作电位对河豚毒素（TTX）敏感。表面积最小（约1600平方微米）的不成熟锥体神经元表现出最大的输入电阻（约1.8千兆欧），而表面积最大（约6200平方微米）的板下层细胞的输入电阻约为1千兆欧。与分叉和不成熟的锥体神经元相比，个体发育较成熟的 Cajal-Retzius 细胞和板下层细胞的动作电位更短且更大。Cajal-Retzius 细胞和板下层细胞对注入去极化电流脉冲的反应是重复不适应且快速发放的放电模式，而不成熟的锥体神经元则表现出强烈的适应性。板下层细胞的动作电位最快，钠电流幅度最大（-714皮安），钠电流密度最高（-38微安/平方厘米），这使得这些细胞能够将传入活动忠实地传递给突触后神经元。虽然所有细胞类型都表达了高电压激活（HVA）钙电流，但它们均未表现出明显的低电压激活钙电流。在不成熟的推测正在迁移的神经元中可观察到最大的峰值（-25.5微安/平方厘米）和稳态（-7.6微安/平方厘米）HVA钙电流密度。相比之下，Cajal-Retzius 细胞和板下层神经元的峰值（-4.9微安/平方厘米）和稳态（<-3.3微安/平方厘米）HVA钙电流密度显著较低。虽然大的HVA钙电流可能促进不成熟神经元的迁移，但低细胞内钙水平可能引发 Cajal-Retzius 细胞和板下层细胞的凋亡。
