Effect of physical activity on hippocampal high affinity choline uptake and muscarinic binding: a comparison between young and old F344 rats

Normal aging has been associated with a progressive decline in hippocampal cholinergic function. In the present study, specific markers of hippocampal cholinergic function, high-affinity choline uptake (HACU) and muscarinic quinuclidinylbenzilate (QNB) binding, were shown to be altered by endurance training (6 months of treadmill running, 5 days/week, 30 min/day). HACU and QNB binding were determined in synaptosomes of endurance trained F344 rats and their age-matched sedentary controls. Comparison of synaptosomes of sedentary rats ages 3 months, 12 months and 25 months (distinguished in this paper as young (Y), middle age (MA) and old (O), respectively) showed maximum HACU at 12 months and subsequent reduction in HACU and QNB binding at 25 months ( P < 0.05). This decline at 25 months is consistent with previous reports of an age-related decline in cholinergic function. Endurance trained rats (trained from 6 months to 12 months of age) showed a reduction ( P < 0.02) in HACU and an increase ( P < 0.05) in QNB binding compared to their age-matched sedentary controls whereas endurance trained rats (trained from 19 months to 25 months of age) showed no significant difference in either parameter from their age-matched sedentary controls. From these results, it appears that while both training and normal aging reduce HACU, the reductions may be different in presynaptic mechanism and postsynaptic consequence.