6-OHDA-induced PD rat model and rotarod test

Rats were deeply anesthetized with 4% chloral hydrate (400 mg/kg, i.p.) and placed in a Stoelting stereotaxic apparatus (Stoelting Co., Kiel, WI, USA). According to a rat brain atlas, 6-OHDA (Sigma, St. Louis, MO, USA), which was dissolved in saline (16 µg/8 µl two side) was injected into the bilateral SNpc at a rate of 0.5 µl/min using a 10 -µl Hamilton syringe. The coordinates for the bilateral SNpc were −5.3 mm anteroposterior, ±1.0 mm mediolateral, and −7.8 mm dorsoventral (from the dura) from the bregma.³² The syringe was left in the SNpc for 4 min and then slowly retracted. Two weeks after surgery, the rotarod test was performed using the Rotarod system (ZH-300, Zhenghua, Anhui Province, China) to test motor function. Each rat was trained for three consecutive days (three times per day) with the speed of the rotor accelerated from 4 to 25 r/min at a rate of 0.5 r/min. After the last training session, rats were tested three times at a speed of 25 r/min, and the longest duration of running time was recorded.