生后早期大鼠视皮层锥体神经元的电学特性

Electrophysiological properties of pyramidal neurons of the early postnatal stage rat visual cortex

目的观察生后早期大鼠视皮层Ⅱ/Ⅲ层锥体神经元的电学特性。方法采用膜片钳全细胞记录结合显微镜直视细胞技术,在急性分离的大鼠视皮层脑片标本上,探讨生后早期大鼠视皮层Ⅱ/Ⅲ层锥体神经元的被动和主动电学特性以及动作电位（AP）的发放特征。结果生后11～13 d（P 11～13）大鼠锥体神经元静息电位为（-56.6±1.8）mV,输入阻抗为（185.4±2.7）MΩ,膜电容为（77.9±2.2）pF,时间常数为（16.9±2.4）ms。AP的幅值和时程分别为（97.7±2.7）mV和（2.3±0.1）ms,阈电位为（-31.8±1.4）mV,后超极化电位为（-65.3±1.3）mV。在受到长的强度不变的去极化电流时,多数神经元表现出明显的锋电位频率适应。AP发放时其稳定放电频率约为第1个放电频率的（30.4±9.4）%。结论 P 11～13大鼠视皮层的锥体神经元的电学特性与成年大鼠不完全相同,大多数的神经元表现出规则放电形式,但其放电频率的适应程度较小。

Objective To investigate the electrophysiological properties of layer Ⅱ/Ⅲ pyramidal neurons of the early postnatal stage rat visual cortex.Methods By using the whole cell patch-clamp recording technique combined with direct visualization of cells,we studied the passive and active electrophysiological properties as well as firing properties of layer Ⅱ/Ⅲ pyramidal neurons in acute rat visual cortical slices.Results Resting membrane potential,input resistance,membrane capacitance and membrane time constant of pyramidal neurons at postnatal days 11-13（P 11-13） were（-56.6±1.8）mV,（185.4±2.7）MΩ,（77.9±2.2）pF and（16.9±2.4）ms,respectively.Action potential amplitude and duration were（97.7±2.7）mV and（2.3±0.1）ms,respectively.Threshold potential was（-31.8±1.2）mV and afterdepolarizing potential was（-65.3±1.1）mV.When presented with long depolarizing current pulse of constant amplitude,most of the neurons exhibited pronounced adaptation of spike frequency.The steady-state firing frequency was（30.4±9.4）% of the first interval firing frequency.Conclusion The electrophysiological properties of layer Ⅱ/Ⅲ pyramidal neurons of the early postnatal stage rat visual cortex are not fully mature.Most of the neurons display regular firing patterns,but the degree of firing frequency adaptation is relatively small.