Elevation of intracellular calcium content in area CA1 of hippocampus is not directly correlated with the development of long-term potentiation.

Electron microscopic localization of calcium-containing mitochondria in stratum radiatum of CAl of hippocampal slices was performed after (1) low-frequency stimulation, (2) high-frequency stimulation, and (3) blocking N-methyl-D-aspartate (NMDA) receptors during high-frequency stimulation. Dendritic mitochondria containing Ca deposits were found in a narrow band of stratum radiatum 280-350 microns distant from stratum pyramidale. Axonal mitochondria containing Ca deposits were evenly distributed in stratum radiatum. The total number of calcium containing-mitochondria was highest in long-term potentiated slices, and less in slices treated with APV; the lowest values were obtained with low-frequency stimulation.