Modelling the Effects of Electrical Coupling between Unmyelinated Axons of Brainstem Neurons Controlling Rhythmic Activity.
Modelling the Effects of Electrical Coupling between Unmyelinated Axons of Brainstem Neurons Controlling Rhythmic Activity.
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DOI：
10.1371/journal.pcbi.1004240
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发表时间：
2015-05
影响因子：
4.3
通讯作者：
Roberts A
中科院分区：
文献类型：
--
作者：
Hull MJ;Soffe SR;Willshaw DJ;Roberts A
精细的无髓鞘轴突之间的缝隙连接可以电耦合大脑神经元组，以同步放电并有助于节律活动。为了探索电耦合的分布和意义，我们模拟了一个分析良好的，小群体的脑干神经元驱动游泳的年轻青蛙蝌蚪。使用30个具有无髓鞘轴突的多室神经元的被动网络来推断：靠近索马的轴突-轴突间隙连接与实验测量的耦合系数最匹配;轴突直径对耦合有很强的影响;大多数神经元通过其他神经元的轴突间接耦合。当加入活性通道时，缝隙连接可使动作电位沿着细轴突的传播不可靠。增加钠离子通道密度和减少钾离子通道密度在最初的轴突节段改善动作电位传播。建模表明，在全细胞记录中观察到的单个尖峰放电到阶跃电流注入不是细胞特性，而是由电耦合引起的分流的动态结果。没有电耦合，射击的人口在去极化电流是不同步的，耦合，人口表现出同步招聘和有节奏的射击。当通过增加模拟感觉通路输入的水平而被激活时，没有电耦合的群体被逐渐招募到非模式化活动。然而，当耦合时，人口被招募到一个有节奏的游泳模式的阈值全部或没有：蝌蚪“决定”游泳。建模强调了精细无髓鞘轴突生理学的不确定性，但是，当被告知生物学数据时，对间隙连接做出了一般性预测：靠近索马的位置;相对较小的数量;神经元之间的许多间接连接;精细轴突中动作电位传播失败的原因;固有放电特性的误导性改变。建模还表明，群体内的电耦合可以同步神经元的募集及其在节律活动期间的起搏器放电。大脑中的一些神经细胞群在它们的过程接触并形成专门的“间隙”连接的地方彼此电连接。电连接最简单的功能是通过避免突触连接处的化学信使造成的延迟，使活动传播得更快。在其他情况下，特别是在更高的大脑区域，更多分散的神经细胞可能通过它们的轴突连接，电耦合的功能不太清楚。为了更好地理解这种类型的电连接，我们建立了一组大脑中电耦合神经细胞的计算机模型，这些神经细胞控制着非常年轻的青蛙蝌蚪的游泳。我们表明，耦合可以是间接的，通过其他成员的群体，并可以深刻地影响的性质的神经细胞，这将是记录在真实的实验。这种耦合的主要作用是使群体的放电同步，因此当蝌蚪受到刺激时，它们都被召集在一起，然后以适合驱动游泳运动的节奏放电。这个简单动物的结果提出了一些问题，这将有助于理解更复杂大脑中的耦合。
Gap junctions between fine unmyelinated axons can electrically couple groups of brain neurons to synchronise firing and contribute to rhythmic activity. To explore the distribution and significance of electrical coupling, we modelled a well analysed, small population of brainstem neurons which drive swimming in young frog tadpoles. A passive network of 30 multicompartmental neurons with unmyelinated axons was used to infer that: axon-axon gap junctions close to the soma gave the best match to experimentally measured coupling coefficients; axon diameter had a strong influence on coupling; most neurons were coupled indirectly via the axons of other neurons. When active channels were added, gap junctions could make action potential propagation along the thin axons unreliable. Increased sodium and decreased potassium channel densities in the initial axon segment improved action potential propagation. Modelling suggested that the single spike firing to step current injection observed in whole-cell recordings is not a cellular property but a dynamic consequence of shunting resulting from electrical coupling. Without electrical coupling, firing of the population during depolarising current was unsynchronised; with coupling, the population showed synchronous recruitment and rhythmic firing. When activated instead by increasing levels of modelled sensory pathway input, the population without electrical coupling was recruited incrementally to unpatterned activity. However, when coupled, the population was recruited all-or-none at threshold into a rhythmic swimming pattern: the tadpole “decided” to swim. Modelling emphasises uncertainties about fine unmyelinated axon physiology but, when informed by biological data, makes general predictions about gap junctions: locations close to the soma; relatively small numbers; many indirect connections between neurons; cause of action potential propagation failure in fine axons; misleading alteration of intrinsic firing properties. Modelling also indicates that electrical coupling within a population can synchronize recruitment of neurons and their pacemaker firing during rhythmic activity. Some groups of nerve cells in the brain are connected to each other electrically where their processes make contact and form specialized “gap” junctions. The simplest function of electrical connections is to make activity propagate faster by avoiding the delays resulting from chemical messengers at synaptic connections. In other cases, especially in higher brain regions where more spread out nerve cells may be connected by their axons, the function of electrical coupling is less clear. To understand this type of electrical connection better we have built computer models of a group of electrically coupled nerve cells in the brain which control swimming in very young frog tadpoles. We show that the coupling can be indirect, via other members of the group, and can profoundly influence the properties of the nerve cells which would be recorded during real experiments. The main role of the coupling is to synchronise the firing of the group so they are all recruited together when the tadpole is stimulated and then fire in a rhythm suitable to drive swimming movements. The results from this simple animal raise issues which will help to understand coupling in more complex brains.
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影响因子：
4.3
作者：
Faisal, A. Aldo;Laughlin, Simon B.
通讯作者：
Laughlin, Simon B.
DOI：
10.1085/jgp.27.1.37
发表时间：
1943-09-20
期刊：
The Journal of general physiology
影响因子：
--
作者：
Goldman DE
通讯作者：
Goldman DE
影响因子：
64.8
作者：
BOSTOCK, H;SHERRATT, RM;SEARS, TA
通讯作者：
SEARS, TA
影响因子：
2.5
作者：
BENNETT, MVL;PAPPAS, GD;NAKAJIMA, Y
通讯作者：
NAKAJIMA, Y
影响因子：
5.5
作者：
Dale, N
通讯作者：
Dale, N