[Changes in electrophysiological properties of pyramidal neuron in motor cortex during the postnatal early development of mice].

To investigate the electrophysiological properties of pyramidal neurons in mouse motor cortex during the early postnatal development.Thirty-six mice were randomly divided into postnatal 1-, 2-, 3-Week and 1-, 2-,3-Month groups (n=6). Membrane properties, action potentials (AP) and spontaneous excitatory postsynaptic currents (sEPSCs) of motor cortex pyramidal neurons were recorded to evaluate the changes in the intrinsic electrophysilogical characteristics by using whole cell patch clamp. Pyramidal neurons and interneurons were distinguished according to the AP firing patterns.Comparing with interneurons, pyramidal neurons exhibited regular spiking (RS) with smaller frequency. During the period of postnatal 1 Week-3 Months, some of the intrinsic membrane properties of motor cortex pyramidal neurons changed. Compared to the 1-Week mice, the resting membrane potential (RMP) of 2-Week decreased significantly (P＜0.01), and the membrane input resistance (Rin) of 1-Month got a hyperpolarization (P＜0.01), and they showed no significant change in the next period, while the membrane capacitance (Cm) showed no significant changes during the whole postnatal development. The AP dynamic properties changed significantly during this period. Compared to the 1-Week mice, the absolute value of the AP threshold and the AP amplitude of the 3-Week increased significantly (P＜0.01), while the spike half width of the 2-Week decreased substantially (P＜0.05), and they showed no significant change in the next period. The sEPSCs frequency and amplitude of 1- Month increased significantly compared to the 1-Week mice(P＜0.01), while during the period of next 1 Month-3 Months, the amplitude and frequency showed no significant change.These results suggest that the motor cortex pyramidal neurons have time-specific eletrophysilogical properties during the postnatal development. The electrophysiological properties can be used as a functional index to detect the degree of neurons maturity, and as a marker to distinguish the pyramidal neurons and interneurons.目的: 研究小鼠生后发育过程中运动皮层锥体神经元电生理特性的变化。方法: 选取出生后不同发育阶段的小鼠共计36只,随机分为1、2、3周龄组(1-, 2-, 3-Week)、1、2、3月龄组(1-, 2-, 3-Month ) (n=6)。应用全细胞膜片钳及生物胞素细胞内标记技术区分锥体神经元与中间神经元,同时记录各组小鼠脑片运动皮层锥体神经元的被动膜特性、动作电位(AP)及兴奋性突触后电流(sEPSCs)。结果: 与中间神经元相比,小鼠运动皮层锥体神经元的AP放电特征表现为规则放电(RS),放电频率较为缓慢。小鼠运动皮层锥体神经元的被动膜特性在出生后发育期间表现为:与1周龄组小鼠相比,2周龄组的静息膜电位(RMP)表现为显著超极化(P＜0.01),2周后再无明显改变;1月龄组的膜输入阻抗(Rin)呈现显著下降的趋势(P＜0.01),在1月龄后无明显变化;膜电容(Cm)无明显变化。 AP在发育早期的变化表现为:与1周龄组小鼠相比,3周龄组AP阈电位绝对值和幅值显著增加(P＜0.01),2周龄组AP半波宽显著降低(P＜0.05),在此之后无显著变化。 sEPSCs随发育过程的变化表现为:1月龄小鼠sEPSCs的频率和幅值相较于1周龄组均显著增加(P＜0.01),在1月后趋于稳定,无显著差异。结论: 在小鼠出生后发育过程中,运动皮层锥体神经元电生理特性的变化存在时间特异性,电生理特性的成熟程度可以作为检测神经元是否成熟的功能学指标,同时电生理特性可以作为皮质中间神经元与锥体神经元区分的标志。.