CYTOCHEMICAL-LOCALIZATION OF CALCIUM IN THE CENTRAL-NERVOUS-SYSTEM OF VERTEBRATES

The ultrastructural localization of endogenous calcium in the brain of a cichlid (Oreochromis mossambicus) was studied using three different cytochemical methods. Ultrathin sections of conventionally embedded material were analyzed with an energy-filtering electron microscope using the techniques of electron energy loss spectroscopy (EELS) and electron spectroscopic imaging (ESI). Calcium signals could be detected, and a high resolution imaging of the calcium distribution was possible. Two of the cytochemical methods using osmiate-bichromate or fluoride as detecting agents produced very similar results with high concentrations of calcium in the endoplasmic reticulum and the extracellular space. Accumulations of calcium were detected especially in the synaptic cleft. In combination with the energy-filtering techniques EELS and ESI these two cytochemical methods are valuable for the study of calcium in central nervous tissue of vertebrates. © 1990.