Antidepressant effects of SiniSan on LPS-induced depression in mice model and the regulation mechanism of SiniSan on Indoleamine2, 3-dioxygenase

Aim To study the influence of SiniSan on the Tryptophan- kynurenine（TRP-KYN）pathway, the activity and content of the key metabolism enzyme indoleamine2, 3-dioxygenase （IDO）. Methods The mice model was established by intraperitoneal injection LPS （ 1 mg · kg^-1 ）. Using ELISA to detect the contents of IFN-γin serum. The content of Tryptophan and kynurenine in brain tissue were detected by using HPLC-MS/MS technique. The mRNA expression level of IDO in brain tissue was detected by using real-time PCR. Results 4 hours after the LPS injection, the immobility time of model group mice prolonged. The content of IFN-~/in serum increased significantly （P 〈 0.05）. Meanwhile, the activity of IDO in brain tissue and the mRNA expression level of IDO increased. SiniSan could short the immobility time of mice, reduced the content of IFN-γin serum （P 〈 0.05）. It could also inhibit the activity of IDO and the expression of mRNA（P 〈 0.01 ）. Conclusion SiniSan blocks the pathway of IDO activation, inhibit the activity of IDO and reduce the content of it. SiniSan produces antidepressant effect by adjusting the TRP-KYN metabolism.