Inhibitory effects of SKI3246, the rhizome extract of Atractylodes japonica, on visceral hypersensitivity in experimental irritable bowel syndrome rat models.

We evaluated the effect of SKI3246, the 50% ethanol extract of the rhizome of Atractylodes japonica, on visceral hypersensitivity, which is a major characteristic feature of IBS. We used various rat models of visceral hypersensitivity to assess the visceral pain responses to colorectal distension (CRD) in comparison with conventional IBS treatments. Oral administration of SKI3246 dose-dependently and significantly attenuated the abdominal withdrawal reflex (AWR) score in a model of acetic acid-induced visceral hypersensitivity. We also found that it reduced the number of abdominal contractions in response to CRD in a model of 2,4,6-trinitrobenzenesulfonic acid-induced visceral hypersensitivity, which was comparable to ramosetron or alosetron. Furthermore, treatment with SKI3246 also increased the pain threshold and abolished the elevated AWR scores to CRD in a rat model of neonatal maternal separation. We presumed that the modulation of the NK2 receptor is involved in the inhibitory activity of SKI3246 on the basis that it significantly inhibited the contraction of the distal colonic muscle induced by neurokinin A, the NK2 receptor agonist. The present results indicate that SKI3246 has the potential to be an effective therapeutic agent for IBS, especially insofar as it can relieve visceral hypersensitivity.