Spread of stimulating current in the cortical grey matter of rat visual cortex studied on a new in vitro slice preparation
Spread of stimulating current in the cortical grey matter of rat visual cortex studied on a new in vitro slice preparation
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DOI：
10.1016/0165-0270(96)00065-9
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发表时间：
1996-08-01
影响因子：
3
通讯作者：
Bullier, J
中科院分区：
文献类型：
--
作者：
Nowak, LG;Bullier, J
脑灰质细胞外电刺激是脑电生理学研究中常用的方法，但对刺激参数的研究较少。本研究探讨了刺激电流在体外大鼠视区17和18 a的传播问题。切片的制备依赖于一个协议，该协议利用了几种已知的手段来限制缺血的影响：氟烷麻醉在手术过程中使用，心内灌注用于降低脑温度，增加脑内葡萄糖和镁的浓度，并降低钙的浓度。刺激电流的传播已确定从强度-距离的关系建立的激活轴突。强度-距离曲线可以用二次关系拟合，表明轴突激活的阈值电流随着轴突与刺激电极尖端之间距离的平方而增加。阈值强度和平方距离（k系数）之间的回归线的斜率从一个轴突到另一个轴突是高度可变的（范围2100- 27500 μ A/mm（2），中位数8850 μ A/mm（2））。这种变异性的一部分与传导速度的差异有关。从这些实验结果中推断出了由给定电流强度激活的轴突分支和轴突初始段的理论数量。
Extracellular electrical stimulation of the cortical grey matter is very often used in electrophysiological studies, but the parameters of the stimulation itself have received only little attention. This study addresses the issue of the spread of stimulating current in rat visual areas 17 and 18a maintained in vitro. The preparation of the slices relied on a protocol making use of several of the means known to limit the effects of ischaemia: Halothane anaesthesia was used during the surgery and intracardiac perfusion was employed to reduce the brain temperature, to increase the intracerebral concentration of glucose and magnesium and to decrease that of calcium. The spread of stimulating current has been determined from strength-distance relationships established for the activation of axons. The strength-distance curves could be fitted by a quadratic relationship, indicating that the threshold current for the activation of an axon increases as the square of the distance separating it from the tip of the stimulating electrode. The slope of the regression line between threshold intensity and squared distance (k coefficient) is highly variable from one axon to another (range 2100-27 500 mu A/mm(2), median 8850 mu A/mm(2)). Part of this variability is related to differences in conduction velocity. The theoretical number of axonal branches and axon initial segments activated by a given current intensity has been extrapolated from these experimental results.