PHYSICAL-ACTIVITY ENHANCES SPATIAL-LEARNING PERFORMANCE WITH AN ASSOCIATED ALTERATION IN HIPPOCAMPAL PROTEIN-KINASE-C ACTIVITY IN C57BL/6 AND DBA/2 MICE

The effects of physical activity on spatial learning performance and associated hippocampal functioning were examined in C57BL/6Ibg (C57) and DBA/2Ibg (DBA) mice. C57 and DBA mice, 3 months of age, were subjected to 8 weeks of a physical activity regime (consisting of moderate-pace treadmill running 5 days/week, 60 min/day, 0% grade, 12 m/min) or remained sedentary in their cages. Mice were then tested on the Morris water maze task for 6 days followed by 12 days of testing on the place learning-set task (8 trials/day with each task). Both C57 and DBA run mice showed no difference in swim speed compared to controls. Hippocampal protein kinase C (PKC) activity was measured in cytosolic, loosely bound, and membrane-bound homogenate fractions. Mice subjected to the physical activity protocol were compared to sedentary controls from the same set of litters. Physical activity produced a 2- to 12-fold enhancement in spatial learning performance on both the Morris (P < 0.0001) and place learning-set (P < 0.02) probe trials in both C57 and DBA mice. DBA mice, which characteristically perform poorly in comparison to C57 mice, were enhanced to perform similarly to C57 control mice. This physical activity-induced enhancement in spatial learning performance was accompanied by alterations in hippocampal bound PKC activity (P < 0.05). These data provide further support for our previous hypotheses of a PKC activity involvement in spatial learning and enhancement of spatial learning performance in rodents by physical activity. In addition, these data indicate that hippocampal PKC activity may be involved in the physical activity-induced enhancement of spatial learning performance.