脉冲激励下轴突产生兴奋后抑制现象的去极化阻滞机制的理论仿真研究  

Theoretical Simulation of Depolarization Block Underpins The Postexcitatory Depression Phenomenon Induced by Pulse Stimulation on Neural Axon

作　　者：韩文娟[1] 陈梦娇[1] 杨明浩[1] 古华光 任维[1] 

机构地区：[1]陕西师范大学生命科学学院,西安710062

出　　处：《生物物理学报》2010年第6期497-504,共8页Acta Biophysica Sinica

基　　金：国家自然科学基金项目(30770701)~~

摘　　要：轴突重复兴奋后表现的兴奋后抑制是机制尚未明了的一种重要的生理现象。在Hodgkin-Huxley方程基础上,引入Na+-K+泵流,并考虑轴突膜内、髓鞘间隙限制区和轴突膜外离子浓度,以及Na+、K+平衡电位的能斯特方程,建立了轴突的电活动模型。低频脉冲激励下,模型产生与刺激脉冲一一对应的动作电位;中等频率脉冲激励下,模型产生兴奋后抑制现象。随着脉冲频率的增加,兴奋后抑制现象出现的频次也增加。在不同刺激强度下,产生兴奋后抑制现象的脉冲频率范围不同。依据数值模拟结果,分析了兴奋后抑制现象的动态过程,以及不同阶段的不同离子机制。揭示了兴奋后抑制是一种去极化阻滞现象,与髓鞘间隙限制区K+、胞内Na+累积和Na+-K+泵的活动密切相关。Postexcitatory depression （PED） exhibited in axon after repetitive excitation is an important physiological phenomenon whose mechanism remains unclear. Based on the Hodgkin-Huxley model, a new model describing electrical activity of axon was built to include Na＋-K＋ pump current, ion distribution along the axon radial and reversal potential of Na＋ and K＋ expressed by the Nernst equation. Under external pulse stimulation with lower frequency, action potential was generated corresponding to each pulse. Stimulation at moderate frequency produced PED phenomenon. The frequency of PED was increased with increasing stimulation frequency. The stimulation frequency can vary with changes in stimulation intensity. The dynamic procedure of PED and different ionic mechanism in different phase of PED were analyzed according to simulation results. PED phenomenon was identified to be a depolarized block phenomenon, closely related to K＋ accumulation in restricted diffusion space of myelin sheath and intracellular Na＋ concentration, and activation of Na＋-K＋ pump.

关 键 词：兴奋后抑制 去极化阻滞 脉冲刺激 Na+-K+泵 神经放电 

分 类 号：Q424[生物学—神经生物学]