Inhibiting fatty acid amide hydrolase normalizes endotoxin-induced enhanced gastrointestinal motility in mice

BACKGROUND AND PURPOSE Gastrointestinal (GI) motility is regulated in part by fatty acid ethanolamides (FAEs), including the endocannabinoid (EC) anandamide (AEA). The actions of FAEs are terminated by fatty acid amide hydrolase (FAAH). We investigated the actions of the novel FAAH inhibitor AM3506 on normal and enhanced GI motility. EXPERIMENTAL APPROACH We examined the effect of AM3506 on electrically-evoked contractility in vitro and GI transit and colonic faecal output in vivo, in normal and FAAH-deficient mice treated with saline or LPS (100 mg.kg(-1), i. p.), in the presence and absence of cannabinoid (CB) receptor antagonists. mRNA expression was measured by quantitative real time-PCR, EC levels by liquid chromatography-MS and FAAH activity by the conversion of [H-3]-AEA to [3H]-ethanolamine in intestinal extracts. FAAH expression was examined by immunohistochemistry. KEY RESULTS FAAH was dominantly expressed in the enteric nervous system; its mRNA levels were higher in the ileum than the colon. LPS enhanced ileal contractility in the absence of overt inflammation. AM3506 reversed the enhanced electrically-evoked contractions of the ileum through CB1 and CB2 receptors. LPS increased the rate of upper GI transit and faecal output. AM3506 normalized the enhanced GI transit through CB1 and CB2 receptors and faecal output through CB1 receptors. LPS did not increase GI transit in FAAH-deficient mice. CONCLUSIONS AND IMPLICATIONS Inhibiting FAAH normalizes various parameters of GI dysmotility in intestinal pathophysiology. Inhibition of FAAH represents a new approach to the treatment of disordered intestinal motility.