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Abstract Background and Aim A glucagon‐like peptide‐1 analog, liraglutide, has been reported to block inflammatory somatic pain. We hypothesized that liraglutide attenuates lipopolysaccharide (LPS)‐induced and repeated water avoidance stress (WAS)‐induced visceral hypersensitivity and tested the hypothesis in rats. Methods The threshold of the visceromotor response induced by colonic balloon distention was measured to assess visceral sensation. Colonic permeability was determined in vivo by quantifying the absorbed Evans blue spectrophotometrically, which was instilled in the proximal colon for 15 min. The interleukin‐6 level in colonic mucosa was also quantified using ELISA. Results Subcutaneously injected LPS (1 mg/kg) reduced the visceromotor response threshold after 3 h. Liraglutide (300 μg/kg subcutaneously) at 15 h and 30 min before injecting LPS eliminated LPS‐induced allodynia. It also blocked the allodynia induced by repeated water avoidance stress for 1 h for three consecutive days. Neither vagotomy nor naloxone altered the antinociceptive effect of liraglutide, but N G ‐nitro‐L‐arginine methyl ester, a nitric oxide synthesis inhibitor, blocked it. LPS increased colonic permeability and the interleukin‐6 level, and the analog significantly inhibited these responses. Conclusions This study suggests that liraglutide blocked LPS‐induced visceral allodynia, which may be a nitric oxide‐dependent response, and was probably mediated by inhibiting pro‐inflammatory cytokine production and attenuating the increased gut permeability. Because the LPS‐cytokine system is considered to contribute to altered visceral sensation in irritable bowel syndrome, these results indicate the possibility that liraglutide can be useful for treating this disease.
Nozu et al. (Tue,) studied this question.