Various exercise intensities differentially regulate GAP-43 and CAP-1 expression in the rat hippocampus.

Exercise intensity is known to affect neuroplasticity. Although corticosterone and lactate levels have been linked to neuroplasticity, the effect of different endurance exercise intensity-dependent production of these biochemicals on the behaviour of hippocampal growth cone markers remains incompletely explored. Here, we investigated the effects of three different endurance treadmill training episodes for six weeks on GAP-43 and CAP-1 expression in the hippocampus of adult male Wistar rats. Our findings showed that mild exercise intensity (MEI) with a lactate production slightly higher than the lactate threshold (LT) is the optimal form of physical activity for elevating GAP-43 without changing CAP-1 expression. It was further observed that high exercise intensity (HEI) with the highest level of corticosterone and lactate production, reduced GAP-43 expression, yet increased CAP-1 expression in the hippocampus. Like HEI, we further identified similar expression patterns for these markers in low exercise intensity (LEI) with blood lactate production below LT and corticosterone level similar to MEI. The findings suggested that in high-intensity exercise, the negative pattern of hippocampal neuroplasticity depends on both corticosterone and lactate levels, whereas in low-intensity exercise, the most important factor determining this negative pattern is the lactate level. Generally, MEI with a lactate production of slightly higher than LT is the most optimal intensity for improving hippocampal neuroplasticity.