Effect of aging on calcium cytosolic concentration in rat cortical synaptosomes

Cytosolic Ca2+ concentrations [( Ca2+]i) were measured in synaptosomes prepared from the cerebral cortex of 3, 16 and 24 month-old male Charles River Wistar rats. Electron microscopy examination demonstrated no morphological differences between the synaptosomes prepared from 3 and 24 month-old rats. Age did not modify [Ca2+]i, as measured by the QUIN 2 technique, both at rest and immediately after depolarization with 50 mM K+. The Ca2+ load following depolarization was cleared in about 13 min in the 3 month-old rats. The rate of clearance was significantly slower both in the (p less than 0.01) and in the 24 month-old (p less than 0.0001). A prolonged calcium influx may be responsible for the slower clearance of Ca2+ load in aged rats.