Objective To explore the possible mechanism of Yuanzhi [Radix Polygalae

远志]-Shichangpu[Rhizoma Acori Tatarinowii

石菖蒲]herb pair in treating attention deficit hyperactivity disorder（ ADHD）. Methods Thirty spontaneous hypertension（ SHR） rats were randomized into a model group

a positive control group and a Yuanzhi-Shichangpu group

with 10 rats in each group. Besides

a normal control group was established with 10Wistar-Kyoto（ WKY） rats. The Yuanzhi-Shichangpu group was given 4. 76 mg/（ kg·d） of Yuanzhi-Shichangpu suspension by gavage. The positive control group was given 2 mg/（ kg·d） of Ritalin suspension by gavage. The normal group and the model group were given 2 ml/（ kg ·d） of 0. 5% sodium carboxymethyl cellulose solution by gavage.Medication was given in rats’ night cycle（ 9: 00—21: 00） for 4 weeks. Spontaneous behavior of rats was evaluated by opening experiment at the time of before medication

medication for 4 weeks and withdrawal for 2 weeks. Rats’ impulsive behavior and learning-memory function were evaluated by elevated plus maze and new object recognition experiments at 4 weeks of medication. Levels of dopamine in prefrontal cortex（ DA） and dopamine transporter（ DAT）were detected at 2 weeks of withdrawal. Results At 4 weeks of medication

rats’ total movement distance and upright number in the opening experiment

as well as the percentage of opening arms times of entering the elevated cross maze and opening arm retention time in the Yuanzhi-Shichangpu group were lower than those in the model group（ P <0. 05）. While in the new object recognition experiment

the preference index for new objects was higher than that in the model group（ P < 0. 05）. At 2 weeks of withdrawal

rats’ total movement distance and upright number in the Yuanzhi-Shichangpu group were lower than those in the model group（ P < 0. 05）

while DA level in prefrontal cortex was higher than that in the model group（ P < 0. 05）. There was no significant difference in DAT levels between the Yuanzhi-Shichangpu group and the model group. of（ P > 0. 05）. Conclusion Yuanzhi-Shichangpu herb pair might improve DA level in prefrontal cortex of ADHD rats

which might be one of the mechanisms of treating ADHD.