To investigate the effects of Baishao（Radix Paeoniae Alba）on rats with irritable bowel syndrome with diarrhea（IBS-D）and irritable bowel syndrome with constipation（IBS-C）.

Sixty-six SD male rats aged 4 weeks were randomly divided into normal control group，IBS-D model group，IBS-D drug group［high，medium and low doses of Baishao（Radix Paeoniae Alba）and pivilium bromide］，IBS-Cmodel group and IBS-C drug group［high，medium and low doses of Baishao（Radix Paeoniae Alba）and moxapride］.Acetic acid stimulation combined with binding stress was used for IBSD modeling，and ice water gavage combined with binding stress was used for IBS-C modeling.The high，medium and low dose groups were administrated with Baishao（Radix Paeoniae Alba）（7.2，3.6，1.8 g/kg body mass，respectively），piverium bromide aqueous solution（13.5 mg/kg）and moxabi aqueous solution（1.35 mg/kg）for 2 weeks，respectively.The weight was performed，the stool was collected，the abdominal withdrawal reflex（AWR）score was performed.The expressions of vasoactive intestinal peptide（VIP）and nuclear transcription factorκB（NF-κB）in ileocecal colon were detected by immunohistochemistry and ELISA.The expression of protease activating receptor 2（PAR2）in intestinal tissues was detected by Western blot.

（1）IBS-D：Baishao（Radix Paeoniae Alba）at high，medium and low doses and piveronium bromide could improve visceral hypersensitivity in model rats（P<0.05，P<0.01，P<0.01，P<0.01，respectively）.Baishao（Radix Paeoniae Alba）at middle and low doses and piveronium bromide could reduce the fecal water content of model rats（P<0.01），but Baishao（Radix Paeoniae Alba）at high dose had no significant effect on reducing fecal water content of model rats（P>0.05）.The weight gain of model group was lower than that of the normal control group（P<0.01），and Baishao（Radix Paeoniae Alba）at high dose could reduce the weight gain of the model group（P<0.05）.Baishao（Radix Paeoniae Alba）at high dose could decrease the expression of NF-κB in model rats（P<0.01）.Baishao（Radix Paeoniae Alba）at high and medium doses could decrease the expression of PAR2 in model mice（P<0.01，P<0.05）.（2）IBS-C：Baishao（Radix Paeoniae Alba）at medium and low doses could improve visceral hypersensitivity of model rats（all P<0.05）.Baishao（Radix Paeoniae Alba）at high dose could increase fecal water content of model rats（P<0.01）.The weight gain of the model group was lower than that of the normal control group（P<0.05），and the drug group had no effect on the body weight of the model rats（all P>0.05）.Baishao（Radix Paeoniae Alba）at high dose and mosapride could decrease VIP expression in model rats（P<0.05，P<0.01）.Baishao（Radix Paeoniae Alba）at low dose could decrease PAR2 expression in IBS-Cmodel rats（P<0.05）.

Baishao（Radix Paeoniae Alba）can improve the visceral hypersensitivity of the rats with IBS-D and IBS-C at the same time，which may be related to the decrease of PAR2 expression.Medium and low doses of Baishao（Radix Paeoniae Alba）can alleviate diarrhea of the rats with IBS-D，while high doses of Baishao（Radix Paeoniae Alba）can promote defecation of the rats with IBS-C，which may be related to the difference of multi-target effects of Baishao（Radix Paeoniae Alba）on different models.