Aging does not alter cytosolic calcium levels of cortical synaptosomes in Fischer 344 rats

Several lines of experimental evidence support an association between altered Ca 2+ regulation and aging. It has been supposed that free cytosolic Ca 2+ concentrations ([Ca 2+] i) may decrease or increase in aged animals. In this study, both resting and KCl-stimulated [Ca 2+] i were measured in purified cortical synaptosomes from young (3 mo.), middle-aged (12 mo.), and old (24 mo.) Fischer 344 rats. Two additional groups of rats were included, one middle-aged and one old which were trained on a treadmill for 6 months prior to experimentation. The [Ca 2+] i was determined using the fluorescent Ca 2+ chelator fura-2. Net KCl-dependent changes (ΔK) in [Ca 2+] i were determined by the difference between stimulatory (100 μM Ca 2+ 60 mM KCl ) and resting (100 μM Ca 2+ 5 mM KCl buffer) conditions among the 3 age groups. Significant increases in [Ca 2+] i were observed in each age group upon depolarization with 60 mM KCl. However, there were no significant age-dependent differences in either resting [Ca 2+] i or KCl-stimulated [Ca 2+] i.