Sudden detraining deteriorates swimming training-induced enhancement of short-term and spatial learning memories in mice.

In the present study, we investigated the effect of swimming training and sudden detraining on learning ability and spatial memory capability and on neurogenesis and brain-derived neurotrophic factor (BDNF) expression in the hippocampus of mice. Male ICR mice were randomly assigned into three groups (n= 15 in each group): the control group, the swimming training group, and the detraining group. The mice in the swimming training group were made to swim (6 days/week, 60 min/day) for 8 weeks. The mice in the detraining group were accomplished the same swimming program for 4 weeks and then discontinued exercise for 4 weeks. In the present results, enhanced short-term and spatial learning memories and increased hippocampal neurogenesis and BDNF expression were observed in the mice of the swimming training group. In contrast, decreased short-term and spatial learning memories were observed in the mice of the swimming detraining group compared to the control level. Hippocampal neurogenesis and BDNF expression were also decreased in the mice of the detraining group near to the control level. Here in this study, we suggest that sudden cessation of exercise training might bring decline of the brain functions.