Diminished calcium currents in aged hippocampal dentate gyrus granule neurones.

Voltage-dependent calcium currents in hippocampal dentate gyrus granule neurons of young adult (4-6 months) and aged (24-26 months) Fischer 344 rats have been examined using single-electrode voltage-clamp techniques. Calcium currents, especially a high threshold slowly inactivating L-type current, were significantly depressed in neurons obtained from aged animals. Furthermore, these age-dependent changes could be reversed by intracellular injection of the calcium chelator, ethylene glycol bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). These results are in agreement with the hypothesis that aging results in a persistent increase in the free cytoplasmic calcium concentration in mammalian central neurons.