Nicholson C, Hounsgaard J
Fed Proc. 1983 Sep;42(12):2865-8.
The brain cell microenvironment includes the extracellular space surrounding the cell together with the cellular elements that define the space. The dense packing of cells in the mammalian nervous system ensures that the extracellular space is narrow but highly complex in geometry. Recent studies with ion-selective micropipettes have revealed that the cerebellar slice can support changes in [K+]o that resemble those seen in the intact preparation. In the slice, [K+]o responses of individual cells can even be resolved. Studies with iontophoretic techniques and quantitative analysis in the slice have shown that the extracellular space has diffusion properties, characterized by a volume fraction and a tortuosity, that are very similar to those seen in the intact animal. These data confirm that the microenvironment in the slice is comparable to that in the intact animal. The diffusion parameters can be used to make predictions about the time necessary for substances to diffuse into slices under various conditions. Such estimates, together with other studies, indicate that it is probably inadvisable to use slices with thicknesses in excess of 300--400 micrometers, and that the bathing conditions can be critical in maintaining slice viability.
脑细胞微环境包括细胞周围的细胞外空间以及界定该空间的细胞成分。哺乳动物神经系统中细胞的密集排列确保了细胞外空间狭窄但几何形状高度复杂。最近使用离子选择性微电极进行的研究表明，小脑切片能够支持类似于完整标本中所见的[K+]o变化。在切片中，甚至可以分辨单个细胞的[K+]o反应。在切片中使用离子电泳技术和定量分析的研究表明，细胞外空间具有扩散特性，其特征在于体积分数和曲折度，这与完整动物中所见的非常相似。这些数据证实切片中的微环境与完整动物中的微环境相当。扩散参数可用于预测在各种条件下物质扩散到切片中所需的时间。这样的估计以及其他研究表明，使用厚度超过300 - 400微米的切片可能是不可取的，并且灌注条件对于维持切片的活力可能至关重要。
