Cytosolic free calcium levels increase with age in rat brain synaptosomes.

Calcium homeostasis in synaptosomes is altered during ageing. The cytosolic free calcium concentration, [Ca2+]i was determined in synaptosomes and crude synaptosomal fractions from 3- and 24-month-old rats with the fluorescent indicator quin-2. The [Ca2+]i were around two times higher in 24-month-old rats than in adults, both under resting conditions and after K depolarization. This difference was still observed after incubation with an endogenous heavy metal chelator. To avoid the calcium buffering effect of quin-2, [Ca2+]i values were determined with the use of a null-point method and with fura-2. These methods confirmed the increase in [Ca2+]i with age in synaptosomes. The increase in [Ca2+]i in nerve endings may be pathologically important in brain ageing.