Until the early 1970s, all basic information on rapid changes in and sequences of membrane ionic permeability during neuronal activity was obtained primarily by the method of voltage clamping individual cells measured in vitro (Katz 1966), or by radioisotopic or other analytical methods which provided data on the total intracellular and extracellular concentrations of different ions. It was not possible to measure the actual ionic concentrations in particular areas of the nervous system during neuronal activity. Even such basic information as the resting [K+]e in the brain was not known, due to the existence of the blood-brain barrier and other barriers. It was not possible to study hypotheses on the regulatory role of small ions during neuronal activity until conventional glass microelectrodes filled with liquid ion exchanger were introduced into neurophysiological research (Walker 1971; Vyskočil and Kříž 1972). In this chapter I would like to present a short survey of the most recent developments and procedures in the measurement of ionic activity in the CNS and receptor organs by means of ion-selective microelectrodes (ISMs).
KeywordsLiquid Membrane Reference Channel Excitable Tissue Receptor Organ Microscopic Control
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