电场对中间神经元亚线性树突整合的调制作用

Modulation Effect of Electric Fields on Sublinear Dendritic Integration of the Interneuron

中间神经元的树突形态大多呈现出空间对称性分布,使得电场在其胞体附近引起的膜电位极化作用微弱,因此大多数研究认为电场对中间神经元难以产生调制作用.然而,电场在中间神经元末端的树突棘位置能够诱发较强的膜电压极化效应,远端的树突极化是否以及如何影响中间神经元的树突整合特性尚不十分清楚.为此本文针对分散和集中空间分布的AMPA类型突触输入,研究了电场对中间神经元全局和局部亚线性树突整合特性的调制作用.为了描述电场作用下树突对AMPA突触输入积分的潜在规律,首先建立了描述中间神经元输入-输出关系的简化电路模型,此模型具有多个被动树突分支且以不均匀细胞外膜电势表征电场诱发的极化效应;其次,基于奇异摄动理论分析了电场调节下的亚线性树突整合的动力学特性,推导出了可描述局部和全局树突整合的阈下输入-输出关系的渐近解析表达式.理论分析结果表明,电场通过改变AMPA突触输入的驱动力调节中间神经元局部以及全局亚线性树突整合特性,调制效应依赖于电场对远端树突的极化程度.相比于局部树突整合,电场对全局树突整合调制更敏感.最后,利用电场作用下具有真实树突形态的海马CA1区中间神经元模型仿真验证了理论分析结果.

Most studies have suggested that the modulatory effect of the electrical field(EF)on the interneuron can be ignored due to the EF-induced weak somatic polarization that results from the symmetric distribution of dendritic morphology.However,EF induces strong polarization at distal dendritic spines of the interneuron.Whether and how these polarizations at the distal dendrites partake in the dendritic integration of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid(AMPA)synapses remain unclear.In this regard,a simplified circuit model with multiple passive dendritic branches was established to capture the dendritic input-output relationship of the interneuron receiving asymmetrically distributed AMPA synapses,in which the inhomogeneous extracellular potentials characterize EF-induced polarizations.The dynamics of sublinear dendritic integration of interneuron were analyzed based on the singular perturbation theory.Our theoretical results showed that the EFs regulated the local and global sublinear dendritic integration properties of the interneuron by altering the driving force of AMPA synaptic inputs,depending on the degree of polarization at the distal dendrites.Additionally,the EF-regulated effect on global dendritic integration has higher efficiency compared to local dendritic integration.The simulation of an interneuron model with realistic dendritic morphology at the hippocampal CA1 in the case of EF stimulation verified the results of theoretical analysis.