Treadmill exercise facilitates synaptic plasticity on dopaminergic neurons and fibers in the mouse model with Parkinson's disease

Exercise for patients with Parkinson's disease (PD) helps to alleviate clinical symptoms such as tremor, balance instability, gait dysfunction, and rigidity. However, molecular mechanism about effect of exercise is poorly unknown. In this study, we investigated effect of exercise in synapse and dendritic spine of nigrostriatal dopaminergic neurons on mice with PD. The C57BL/6J male mice (n = 40) were divided by sham group, sham-exercise treated group, 1-Methyl-4-phenyl-l,2,3,6-tetrahydropyridine (MPTP) treated group, and MPTP-exercise treated group. For exercise treatment, the mice were put on the treadmill to run for 8 m/min, 30 min/day, and 5 times/week for 2 weeks. Coordination ability was checked by rota rod test. Expression of tyrosine hydroxylase (TH), synaptophysin, and post-synaptic density protein 95 (PSD-95) was confirmed at substantia nigra pars compacta (SNpc) or striatum using western blotting, or immunohistochemistry. To check dendritic spine in striatum, we used Golgi staining. The results revealed that MPTP treated group displayed poor coordination ability compared with sham group. However, MPTP-exercise treated group showed good coordination ability compared with MPTP treated group. As well as, we also found that MPTP-exercise group increases expression of synaptophysin, PSD-95, TH, and dendritic spine in nigrostriatal dopaminergic neurons and fibers than MPTP treated group (p < 0.05). Our findings suggest that exercise may give beneficial effects to patients with PD by facilitating synaptic plasticity and increasing dendritic spines.