Treadmill exercise alleviates depressive symptoms in rotenone-induced Parkinson disease rats

Abstract

Parkinson disease (PD) is characterized by selective loss of the dopa-minergic neurons. The symptoms of depression following PD are close-ly associated with reduced activity of the serotonergic system in the dorsal raphe. We explored the anti-depressive effect of exercise and its possible mechanism using the rotenone-induced PD rats. PD rats were induced by subcutaneously injection with rotenone for 14 days. The rats in the exercise groups were made to run on a treadmill for 30 min once a day during 14 consecutive days. Forced swimming test, immunohisto-chemistry for serotonin (5-hydroxytryptamine, 5-HT), tryptophan hydrox-ylase (TPH), and western blot for serotonin 1A (5-HT1A) receptor were conducted. Injection of rotenone induced PD rats. PD rats showed de-pressive state and treadmill exercise ameliorated this depressive state. 5-HT, TPH, and 5-HT1A receptor expressions in the dorsal raphe were suppressed by rotenone injection and treadmill exercise increased the expressions of 5-HT, TPH, and 5-HT1A receptor in the rotenone-injected rats. The present results show that treadmill exercise ameliorated de-pressive symptoms in the rotenone-induced PD rats. The antidepres-sive effect of treadmill exercise might be ascribed to the enhancement of serotonergic function through upregulation of 5-HT1A expression in the dorsal raphe.