生后早期大鼠初级视皮层Ⅰ层中间神经元电学特性研究

Electrical Properties of Interneurons in the Neocortical Layer Ⅰ of the Visual Cortex of the Postnatal Rats

目的:研究视觉发育可塑性关键期内大鼠初级视皮层Ⅰ层中间神经元的电学特性,以期通过分析其电学特性进一步区分神经元的类型。方法:采用脑片膜片钳全细胞记录技术,观察13~15天SD大鼠初级视皮层Ⅰ层单眼反应区(Oc1M)中间神经元的被动、主动电学特性和动作电位的发放特征。结果:大鼠初级视皮层Ⅰ层中间神经元动作电位的后电位表现为后去极化和后超极化两种形式。后去极化的幅度能够达到15.11±3.02 mV;而后超极化的幅度为-6.22±0.53 m V。基于后电位的不同,将Ⅰ层中间神经元分为后去极化神经元(ADPNs)和后超极化神经元(AHPNs)两类。对两类神经元的电学特性进行统计比较发现,ADPNs具有较高的静息电位、较低的阈电位和较高的能障(P<0.05)。此外,两类神经元在动作电位峰幅值、最大下降斜率、峰展宽以及频率适应性上均具有显著性差异(P<0.05)。结论:在视觉发育可塑性关键期内,大鼠初级视皮层Ⅰ层中间神经元可根据其电学特性分为ADPNs和AHPNs两种类型,二者可以进一步通过其被动和主动电学特性以及动作电位发放特性加以区分。

Objective To investigate the electrophysiological properties of layerⅠinterneurons during the critical period of developmental plasticity in the primary visual cortex(area Oc1 M)of rats,so as to further distinguish the types of layerⅠinterneurons by analyzing their electrical properties.Methods Whole-cell patch-clamp recordings were used to study the passive and active electrical properties as well as firing features of layerⅠinterneurons in the monocular region of the primary visual cortex(area Oc1 M)of rats.Results Two types of after-potentials,after-depolarization and after-hyperpolarization,were found in the action potentials of layerⅠinterneurons of the primary visual cortex.The degree of the after-depolarization could reach 15.11±3.02 mV,and the amplitude of the after-hyperpolarization was-6.22±0.53 mV.In view of the after-potentials,the layer I interneurons could be divided into two distinct types,after-depolarization neurons(ADPNs)and after-hyperpolarization neurons(AHPNs).Statistical analysis of the passive and active electrical properties of the two types of interneurons showed that the ADPNs had a higher resting membrane potential and energy barrier,but a lower voltage threshold than AHPNs(P<0.05).Moreover,there were significant differences between them in the reduction of the peak amplitude,maximum descending slope,width of the peak and frequency adaptation(P<0.05).Conclusion During the critical period of the developmental plasticity of rats,the layerⅠinterneurons of the primary visual cortex are of two major types,ADPNs and AHPNs,according to their electrical properties.These two types of interneurons can be further distinguished by analyzing their passive and active electrical properties as well as firing features.