Use of Ion-Selective Microelectrodes and Voltammetric Microsensors to Study Brain Cell Microenvironment

The dense aggregation of cells that make up the brain and spinal cord has always prompted discussion about the nature of the interstitial region. This region was termed the “extracellular space” and for many years its extent, and even its existence, was widely disputed. Later the concept of the extracellular space became extended and deepened, primarily because of Schmitt and Samson (1969), who recognized that the space was not merely a saline-filled gap between cells, but rather that it was a complex region defined by the membranes of the bounding cells. These membranes were adorned with a rich variety of long-chain proteoglycans that extended into the extracellular space, potentially endowing it with unusual properties. In recognition of potential functional importance of this domain, the term “brain cell microenvironment,” henceforth abbreviated to BCM, was introduced (Schmitt and Samson, 1969).