Dual effects on constipation and diarrhea: protective potential of Radix Inulae lactones on irritable bowel syndrome

Abstract

Radix Inulae (RI) is commonly used to treat upper body pain, emesis, diarrhea and parasitic diseases in China. In the present study, Wistar rats were administered with chronic durative stimulus or acute chemical stimulus to induce constipation-IBS (C-IBS) or diarrhea-IBS (D-IBS) rodent models, which then received RI lactones (10, 30, 90 mg kg⁻¹) to investigate the effect of RI lactones on experimental models of C-IBS and D-IBS and the underlying action mechanism. Then mice were administered with neostigmine or atropine to establish models of abnormal gastrointestinal motility, on which 123 mg kg⁻¹ RI lactones was used to further test the effect on gastrointestinal motility. The results showed that RI lactones significantly increased the defecation and stool moisture capacity of C-IBS rats (P < 0.001), and significantly reduced loose stool percentage of D-IBS rats (P < 0.05). RI lactones increased the abdominal withdrawal reflex (AWR) score in C-IBS rats (P < 0.05) and decreased it in D-IBS rats (P < 0.05) in a dose-dependent manner. An enzymatic immunoassay study revealed that RI lactones treatment significantly down-regulated serum NO levels of C-IBS rats (P < 0.05) and up-regulated NO levels of D-IBS rats (P < 0.05). RI lactones also reduced serum serotonin (5-HT) (P < 0.001) and distal colon VIP concentration (P < 0.05) of both IBS rats. In addition, a gastrointestinal motility study verified that RI lactones treatment bilaterally regulated neostigmine and atropine induced bowel disturbance. These results demonstrated that RI lactones may relieve C-IBS and D-IBS symptoms through regulating neurotransmitters and gastrointestinal hormones (NO, 5-HT and VIP) and correcting the propulsive movement of the intestine.