Treadmill exercise improves spatial learning ability by enhancing brain-derived neurotrophic factor expression in the attention-deficit/hyperactivity disorder rats

Attention-deficit/hyperactivity disorder (ADHD) patients show learning difficulty and impulsiveness. Exercise is known to improve learning ability and memory function. In the present study, we investigated the duration-dependence of the effect of treadmill exercise on spatial learning ability in relation with brain-derived neurotrophic factor (BDNF) expression in ADHD rats. For this study, radial 8-arm maze test and western blot for BDNF and tyrosine kinase B (TrkB) were performed. Spontaneous hypertensive rats were used as the ADHD rats and Wistar-Kyoto rats were used as the control rats. The rats in the exercise groups were forced to run on a treadmill for 10 min, 30 min, and 60 min once a day for 28 consecutive days. ADHD rats displayed impairment of spatial learning ability, in contrast treadmill exercise ameliorated impairment of spatial learning ability. Treadmill exercise for 30 min per day showed most potent ameliorating effect on impairment of spatial learning ability. BDNF and TrkB expressions in the hippocampus were decreased in the ADHD rats, in contrast treadmill exercise enhanced BDNF and TrkB expressions. Treadmill exercise for 30 min and for 60 min per day showed enhancing effects on BDNF and TrkB expressions. Treadmill exercise alleviated deficits in the spatial learning ability through enhancing BDNF and TrkB expressions in the ADHD rats. Treadmill exercise for 30 min per day can be considered as the most effective therapeutic modality for the ADHD symptoms.