EFFECT OF PHYSICAL-TRAINING ON THE AGE-RELATED-CHANGES OF ACETYLCHOLINESTERASE-POSITIVE FIBERS IN THE HIPPOCAMPAL-FORMATION AND PARIETAL CORTEX IN THE C57BL 6J MOUSE/

We investigated the effect of a moderate amount of prolonged physical training initiated at 3 months of age on the age-related changes of th e hippocampal and cortical cholinergic fibers. A total of 80 male C57B L/6J mice were divided into five groups which were trained (including adult and old trained, AT and OT), sedentary (adult and old sedentary, AS and OS) and young (Y). From 3 months old, the mice of the trained groups were treated with a voluntary running wheel for I h each day, 5 days per week. AT had been trained up to 13-month-old whereas OT up t o 24 months old. At the same time, the mice of the sedentary groups we re put in immobilized wheels. We set the criterion for effective train ing in the trained mice such that the heart-to-body weight ratio shoul d be at least 2 S.D. above the mean in the age-matched groups. Using A ChE histochemistry and stereology, the AChE-positive fibers were analy zed quantitatively in the molecular layers in CAI, CA3 and the dentate gyrus of the hippocampal formation, and in III, V layers in the motor and somatosensory cortex. Comparison of Y, AS and OS (3, 13 and 24 mo nths of age) showed minimum AChE-positive fiber density in the hippoca mpal formation and the cortex in OS (P < 0.01). After 10 and 21 months of running, the AChE-positive fibers in all regions examined in the t rained groups were significantly increased compared to their age-match ed controls (P < 0.05 or 0.01). In the hippocampal formation, the incr ease was about 17% in AT and 23% in OT, whereas, in the cortex, it was 13% in AT and 22% in OT. These results indicated that a moderate amou nt of prolonged physical training could modify the age-related loss of cholinergic fibers in the hippocampal formation and cortex, furthermo re the modified loss of cholinergic fibers might be associated with th e regeneration of hippocampal and cortical cholinergic fibers stimulat ed by chronic running. (C) 1998 Elsevier Science Ireland Ltd. All righ ts reserved.