大鼠出生后内侧膝状体腹侧部神经元电生理和形态学特性的发育变化

Changes in electrophysiological and morphological properties of neuron in the ventral partition of medial geniculate body during the postnatal development of rats

本实验采用脑片膜片钳全细胞记录和生物胞素(biocytin)组化染色相结合的技术,研究出生后(postnatal day,P)3～30日龄大鼠(P3～30)内侧膝状体腹侧部(ventral partition of medial geniculate body,MGBv)神经元的电生理和形态学特性的发育变化.结果显示:(1)在P3～30的发育过程中,MGBv神经元的静息膜电位自-40 mV降至-67 mV(P＜0.01);输入阻抗由1 832MΩ降至806 MΩ(P＜0.01);时间常数由2.55 ms降至0.96 ms(P＜0.01).同时,动作电位的幅度、阈值和时程也表现出显著差异(P＜0.01);(2)K+通道阻断剂4-AP使P6的MGBv神经元诱发动作电位数目减少,幅度降低,时程变宽,并使P16的动作电位幅度逐渐降低至去极化脉冲终末达到平台电位,而Ca2+通道阻断剂CdCl2仅引起P16的MGBv神经元动作电位的幅度降低,时程延长;(3)在用biocytin标记的MGBv神经元观察到,幼稚MGBv蓬丛样神经元(tufted neuron)胞体呈圆形或椭圆形,而随着出生后日龄的增长,胞体逐渐变成梭形.轴突出现较早,树突的发育相对较晚,但其发育变化更为显著和复杂.以上结果提示,大鼠出生后MGBv神经元电生理和形态学特性仍有显著的发育变化,且两者明显相关.

We investigated the electrophysiological and morphological characteristics of the neurons in the ventral partition of medialgeniculate body (MGBv) in the rat during postnatal development (postnatal day 3~30, P3~30) with whole-cell patch clamp recordingand intracellular labeling technique. The results are as follows: (1) There was an increase in the negativity of the resting membranepotential, a decrease in the input resistance and the time constant of the MGBv neurons of rats during the postnatal development; theamplitude, threshold and duration of the action potentials were also different on different postnatal days; (2) During the postnataldevelopment, the changes in voltage-dependent ion channels dramatically influenced the waveform of action potential in the MGBvneurons. Application of 4-AP, a K+-channel blocker, reduced the amplitude and prolonged the durations of the action potentials in P6neurons, and inactivated the neurons at the end of the pulse in P16 rats. Application of CdCl2 to block the voltage-dependent Ca2+-channel decreased the amplitude and increased the duration of the action potential in P16 rats; (3) Biocytin staining revealed thatimmature MGBv cell had smaller somata and short, simple dendritic aborization. During postnatal development, the matured neuronshad oval somata and 3~4 primary dendrities that radiated irregularly and projected outside the section; spines also appeared on thedendrites of the mature neurons. These results reveal that the morphologic and electrophysiological properties are not matured duringearly postnatal development, and that the electrophysiological and morphological features of the developing MGBv neurons are interrelated.