Ethnopharmacological relevance: Ningdong granula (NDG) is a traditional Chinese medicine (TCM) preparation for the treatment of Tourette's syndrome (TS).
Aim of the study: To explore the effects of NDG on stereotyped behavior, homovanillic acid (HVA) in sera, dopamine (DA) and dopamine D2 receptor (DRD2) in striatum in TS rats.
Materials and methods: Sixty-four rats were randomly divided into control group and three experimental groups. TS rat models were induced by intraperitoneal injection (i.p.) of Apomorphine (Apo, 2 mg/kg) in the experimental groups. After Apo i.p., rats were intragastrically injected (i.g.) with NDG at 370 mg/kg (NDG+Apo group), haloperidol (Hal) at 1.0 mg/kg (Hal+Apo group), and normal saline (0.9%) at 10 ml/kg (control group and Apo group), respectively, once a day for 12 weeks. The behaviors of the rats were observed and recorded each day. After 12 weeks, all rats were sacrificed and sera and striatum were collected. The levels of HVA in sera, DA in striatum were examined by ELISA, and the expression of DRD2 mRNA in striatum was measured by RT-PCR.
Results: NDG could increase the HVA content in sera (P<0.05), meanwhile downregulate the expression of DRD2 mRNA in striatum (P<0.05), and inhibit the stereotyped behaviors induced by Apo (P<0.01) in TS rats, the same effects with Hal. NDG could also reduce the DA content in striatum (P<0.01), while Hal could not.
Conclusions: NDG could effectively inhibit the stereotyped behaviors in TS rats, and the mechanisms may be related to the suppression of DA system by increasing the content of HVA in sera, decrease the content of DA and repressing the expression of DRD2 mRNA in striatum.