The role of divalent cations, particularly of calcium, has gained increasing interest as a charge carrier and in processes such as regulation of enzymatic activities, in secretions of humoral transmitters and initiation of muscle contraction. The role of calcium has become very important in manifesting the bursting activity of neurons by various electrophysiological techniques, especially by voltage clamping. The distribution of calcium compared with the ultrastructure of nerve cells, however, has not been widely investigated. Analysis by the electron probe X-ray microanalyser(EPXMA) makes this type of research easier. To determine the relationship between calcium localization within the neuron and cellular function, we tried to make an intracellular calcium distribution map of the normal state and that during bursting activity by the computer controlled EPXMA. We also detected the chemical shift between the different states of cellular function caused by the intracellular calcium binding state.
