Intracellular measurement of ionic activity

Abstract The measurement of intracellular ionic activity is crucial to a quantitative understanding of neuronal function. Intracellular ion-sensitive microelectrodes (ISMs) can now be routinely made which are capable of determining the ionic activities of Na + , K + , Cl − , H + and Ca 2+ and of monitoring their changes even in small neurones. This article outlines some of the theoretical and practical aspects underlying the use of ISMs, and provides details of some applications. Interested readers should also consult the recent article by Charles Nicholson on extracellular measurement ( TINS 1980, pp. 218-218).