Environmental Impacts on Spiking Properties in Hodgkin-Huxley Neuron with Direct Current Stimulus

Based on the well accepted Hodgkin-Huxley neuron model, the neuronal intrinsic excitability is studied when the neuron is subject to varying environmental temperatures, the typical impact for its regulating ways. With computer simulation, it is found that altering environmental temperature can improve or inhibit the neuronal intrinsic excitability so as to influence the neuronal spiking properties. The impacts from environmental factors can be understood that,the neuronal spiking threshold is essentially influenced by the fluctuations in the environment. With the environmental temperature varying, burst spiking is realized for the neuronal membrane voltage because of the environment-dependent spiking threshold. This burst induced by changes in spiking threshold is different from that excited by input currents or other stimulus.     

关于电压、电势和电势差概念的理解

文章讨论了稳定涡旋电场中导体上的电压,并把该情况及似稳条件下导体上的"电势""电势差"与静电场中的电势、电势差作了比较。结果表明:只存在静电场时,空间任一点有电势,两点间有电势差;存在涡旋电场时,在一定条件下(形成稳定电流和似稳电流时)在导体上任一点有"电势",只在由导体连接着的两点间有"电势差"。当电场为只由静止电荷激发的静电场,此时一点的电势值与零点的选择有关,电势差与积分路径无关;当电场为全部电场中的保守场部分时,一点的"电势"值与零点的选择有关,"电势差"也与积分路径无关。两点间电势差是单位正电荷从一点经任意路径移到另一点时外力克服静电力做功而增加的能量,即静电势能的增量;两点间"电势差"是单位正电荷从导体上任一点经导体中的任意路径移到另一点时获得的(净)能量,是外力所做的功除去发热剩余的能量,数值上恰等于静电势能的增量。     

离子与通道相互作用对NaK 通道通透特性影响的研究

以NaK 通道的三维精细结构为基础,从理论上阐述了NaK 通道对钠离子、钾离子、铷离子以及钙离子的通透机理,钡离子可以作为NaK 通道阻断剂的微观机理,我们的研究结果表明,通道与离子的相互作用是决定通道对不同离子选择性的基础, 反映通道与离子相互作用的位能曲线是通道对不同离子通透性的外在表现. 关键词： NaK 通道 密度泛函 布朗动力学 通透性     

Properties of Hydrated Alkali Metals Aimed at the Ion Channel Selectivity

The hydration structure properties of different alkali metal ions with eight water molecules and potassium ions with different numbers of water molecules are studied using the mixed density functional theory, B3LYP, with 6-3110 basis set. The hydration structures are obtained from structure optimization and the optimum numbers of water molecules in the innermost hydration shell for the alkali metal ions are found. Some useful information about the ion channel selectivity is presented.     

Electrostatic Interactions Determining the Selectivity of KcsA Channel and Its Mutants

We perform the density functional theory and Brownian dynamics simulations based on the three-dimensional structure of the WT KcsA channel and its mutants. Our data suggest that the electrostatic interactions between the channels and cations, within the signature sequence of K^＋ channels, determine the selectivity of the channel.     

The synchronization of FitzHugh--Nagumo neuron network coupled by gap junction

It is well known that the strong coupling can synchronize a network of nonlinear oscillators. Synchronization provides the basis of the remarkable computational performance of the brain. In this paper the FitzHugh-Nagumo neuron network is constructed. The dependence of the synchronization on the coupling strength, the noise intensity and the size of the neuron network has been discussed. The results indicate that the coupling among neurons works to improve the synchronization, and noise increases the neuron random dynamics and the local fluctuations; the larger the size of network, the worse the synchronization. The dependence of the synchronization on the strength of the electric synapse coupling and chemical synapse coupling has also been discussed, which proves that electric synapse coupling can enhance the synchronization of the neuron network largely.     

The spike timing precision of FitzHugh-Nagumo neuron network coupled by gap junctions

It has been proved recently that the spike timing can play an important role in information transmission, so in this paper we develop a network with N-unit FitzHugh--Nagumo neurons coupled by gap junctions and discuss the dependence of the spike timing precision on synaptic coupling strength, the noise intensity and the size of the neuron ensemble. The calculated results show that the spike timing precision decreases as the noise intensity increases; and the ensemble spike timing precision increases with coupling strength increasing. The electric synapse coupling has a more important effect on the spike timing precision than the chemical synapse coupling.     

钾离子通道布朗动力学研究

结合钾离子通道的三维精细结构，从第一性原理出发，在充分考虑电子相互作用的基础上，采用密度泛函方法计算得到了钾通道的位能曲线；以此作为钾通道布朗动力学模型的力场参数，应用布朗动力学方法研究了钾离子通道的动力学特征，得到了一些有益的结果。In the paper, based on the first principle and the X-ray structure of the potassium ion channel, the potential curve is calculated by the density functional theory. And forced by the potential, the dynamical properties of K channels are also studied.