Aim of study:Xiao-Ban-Xia-Tang (XBXT) is a traditional Chinese herbal formula which has been widely used as an anti-emetic to treat vomiting induced by many conditions.In the recent decades,XBXT is also used as an effective therapy to prevent and treat chemotherapy-induced nausea and vomiting (CINV) in clinic,but its underlying mechanism is not fully explored.In the present study,we have investigated the antiemetic efficacy of XBXT on acute and delayed CINV in rat pica model induced by cisplatin,and measured the contents of substance P in rat serum,ileum and medulla oblongata,the mRNA expression levels of preprotachykinin A (PPTA) and neurokinin 1 (NK1) receptor in rat ileum and medulla oblongata.Material and methods:The chemotherapy rat pica model was established by i.p.injection of 6 mg/kg cisplatin.The Wistar rats were randomly divided into normal control group,XBXT control group (1.6g/kg),cisplatin model group,positive drug ondansetron group (2.6 mg/kg),XBXT high (3.2 g/kg) and low (1.6 g/kg) dose groups.The rats in ondansetron group,XBXT control group,XBXT high and low dose groups were respectively given 2.6mg/kg/d ondansetron,1.6,3.2 and 1.6g/kg/d XBXT by oral gavage before modeling th and then twice a day.The rats in normal control group and model group were gavaged with equal volume of distilled water.Kaolin consumptions were weighed and calculated once per 12h.After modeling 24h and 72h,substance P contents in rat serum,ileum and medulla oblongata were measured by CLIA and ELISA,and PPTA and NKI receptor mRNA expression levels in rat ileum and medulla oblongata were measured by Real-time PCR.Results:Kaolin consumptions in model group were significantly increased.2.6mg/kg ondansetron,3.2 and 1.6g/kg XBXT could significantly inhibit kaolin consumptions in cisplatin-treated rats.3.2 and 1.6g/kg XBXT can reduce substance P contents in serum,ileum and medulla oblongata,and inhibit the abnormal mRNA expression of PPTA and NKI receptor in ileum and medulla oblongata of rats under chemotherapy.1.6g/kg XBXT showed no effect on substance P contents and PPTA and NKI receptor mRNA expression levels in normal rats.Conclusions:The results suggest that the mechanism of XBXT on the prevention and treatment of CINV may be related to the decrease of substance P contents and down regulation of NKI receptor mRNA expression induced by cisplatin.