Attention-deficit/hyperactivity disorder (ADHD) involves clinically heterogeneous dysfunctions of sustained attention, with behavioral hyper-activity and impulsivity. The exact underlying mechanisms of ADHD are not known, however, impairment of dopaminergic system in the nigrostriatal pathway was suggested as the one of the possible mechanisms of ADHD. Tyrosine hydroxylase (TH) is the rate-limiting enzyme that is involved in the synthesis of dopamine. Spontaneous hypertensive rats have been used as the animal model for ADHD. Physical exercise is known to restore the brain functions disrupted by several neurode-generative and psychiatric disorders. In the present study, we investigated whether treadmill exercise exerts therapeutic effect on ADHD. Social interaction test for the evaluation of impulsivity was performed using spontaneous hypertensive rats. TH expressions in the substantia nigra and striatum were evaluated by immunohistochemistry. In the present results, the rats of ADHD model showed hyper-social behaviors. TH expressions in the substantia nigra and striatum were decreased in the rats of ADHD model. Treadmill exercise alleviated hyper-social behaviors in the ADHD rats. TH expressions of ADHD rats were also enhanced by treadmill exercise. Here in this study, we showed that treadmill exercise effectively alleviates the ADHD-induced symptoms through enhancing of TH expression in the brain.
Keywords: Attention-deficit/hyperactivity disorder; Social interaction; Striatum; Substantia nigra; Treadmill exercise; Tyrosine hydroxylase.