The effect of age on calcium dynamics in rat brain in vivo

Different biochemical changes accompany development and ageing. However, the time frame for a particular biochemical change may be different than that for another. In the ageing brain, neurological deficits related to ageing have been suggested to be due to a breakdown of calcium (Ca + +) homeostasis, and an increase in intracellular Ca + +. To understand the dynamics of calcium in CNS in relation to normal ageing, we have determined 45Ca + + uptake by the different regions of brain in young (3 months) and aged (15 months) rats after a single i.v. injection of 90 μCi/kg 45Ca + +. In the aged group, the initial plasma contents of the tracer were higher than in the young rats (3 months). The mean values of uptake (as fraction of injected dose/g × 10 5) of 45Ca at different sites were higher in the 15-month-old animals than in the young rats (viz. cortex: 50 vs. 26; hippocampus: 90 vs. 46 and putamen: 54 vs. 30 at 120 min). Computer simulation of the uptake data indicated that the values of most of the fractional transport rates were similar or lower in the aged compared to the controls. However, the steady state ratio of intra/extracellular Ca + + was higher in the 15-month-old animals, suggestive of intracellular accumulation of Ca + +.