Physical training modifies the age-related decrease of GAP-43 and synaptophysin in the hippocampal formation in C57BL/6J mouse.

We investigated the effect of a moderate amount of prolonged physical training initiated at 3 months of age on the expression of GAP-43 and synaptophysin in the hippocampal formation. C57BL/6J mice were divided into three groups which were trained (24 months old), sedentary (24 months old) and young (3 months old). From 3 months of age on, mice of trained group were treated with voluntary running wheel for 1 h each day (5 days per week) until 24 months of age (21 months running), whereas mice of sedentary group were put in immobilized wheels for the same time. Using immunohistochemistry and image analysis system, GAP-43 and synaptophysin were analysed quantitatively in the CA1, CA3 areas and the dentate gyrus of the hippocampal formation. As compared with young mice, the densities of GAP-43 and synaptophysin immunostaining showed a significant decrease in the hippocampal formation in sedentary group (P<0.01). After 21 months of running, the densities of GAP-43 and synaptophysin immunostaining significantly increased in the examined areas of the hippocampal formation in trained mice compared to their age-matched sedentary controls (P<0.05, 0.01). These results indicate that a moderate amount of prolonged physical training could modify the age-related decrease of the expression of GAP-43 and synaptophysin in the hippocampal formation, and that the increased expression of GAP-43 and synaptophysin might be associated with the anatomical sprouting and synaptogenesis.