Independence of extracellular tortuosity and volume fraction during osmotic challenge in rat neocortex
Independence of extracellular tortuosity and volume fraction during osmotic challenge in rat neocortex
复制标题
DOI：
10.1113/jphysiol.2002.017541
复制
发表时间：
2002-07-15
影响因子：
5.5
通讯作者：
Nicholson, C
中科院分区：
文献类型：
--
作者：
Kume-Kick, J;Mazel, T;Nicholson, C
脑细胞外间隙（ECS）的结构特性由迂曲度（lambda）和体积分数（alpha）总结。为了确定这两个参数是否是独立的，我们通过改变NaCl含量来改变大鼠皮质切片的浴介质的渗透压来改变ECS的大小。使用四甲基铵（TMA（+））的实时离子电泳法从扩散测量中提取λ和α值。在正常培养基（305 mosmol kg（-1））中，λ的平均值为1.69，α的平均值为0.24。将渗透压降低至150 mosmol kg（-1），λ增加至1.86，α降低至0.12。将渗透压摩尔浓度增加至350 mosmol kg（-1），将λ降低至约1.67，即使渗透压摩尔浓度进一步增加至500 mosmol kg（-1），λ也保持不变。相反，随着渗透压摩尔浓度的增加，α稳定增加至0.42。与先前发表的实验比较，采用3000 M-r葡聚糖来测量λ，显示出与TMA（+）相同的行为，包括在高渗介质中相同的常数λ，但在低渗溶液中具有更陡的斜率。这些数据表明，λ和α的行为不同的ECS几何形状的变化。当alpha减小时，lambda增加，但当alpha增加时，lambda迅速达到恒定值。以前的模型，允许细胞的形状改变渗透挑战过程中可以占定性的平台行为的λ。
The structural properties of brain extracellular space (ECS) are summarised by the tortuosity (lambda) and the volume fraction (alpha). To determine if these two parameters were independent, we varied the size of the ECS by changing the NaCl content to alter osmolality of bathing media for rat cortical slices. Values of lambda and alpha were extracted from diffusion measurements using the real-time ionophoretic method with tetramethylammonium (TMA(+)). In normal medium (305 mosmol kg(-1)), the average value of lambda was 1.69 and of alpha was 0.24. Reducing osmolality to 150 mosmol kg(-1), increased lambda to 1.86 and decreased alpha to 0.12. Increasing osmolality to 350 mosmol kg(-1), reduced lambda to about 1.67 where it remained unchanged even when osmolality increased further to 500 mosmol kg(-1). In contrast, alpha increased steadily to 0.42 as osmolality increased. Comparison with previously published experiments employing 3000 M-r dextran to measure lambda, showed the same behaviour as for TMA(+), including the same constant lambda in hypertonic media but with a steeper slope in the hypotonic solutions. These data show that lambda and alpha behave differently as the ECS geometry varies. When alpha decreases, lambda increases but when alpha increases, lambda rapidly attains a constant value. A previous model allowing cellular shape to alter during osmotic challenge can account qualitatively for the plateau behaviour of lambda.