Effect of inhibition of inducible nitric oxide synthase and guanylyl cyclase on endotoxin-induced delay in gastric emptying and intestinal transit in mice

Nitric oxide (NO) is postulated to play a role in endotoxin-incluced ileus. We investigated the effect of selective blockade of inducible NO synthase (iNOS) and guanylyl cyclase on endotoxin-induced ileus in mice. Thirty minutes before injection of lipopolysaccharides (LPS), mice were pretreated with L-NAME (Nomega-nitro-L-arginine methyl ester, non-selective NOS inhibitor), 1400W (N-(3-(aminomethyl)benzyl)acetamide, selective iNOS inhibitor), ODQ (1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one, guanylyl cyclase inhibitor), dimethyl sulfoxide (DMSO, vehicle), or dexamethasone. After 18 h, general well being deteriorated and the mice developed hypothermia and a significant delay in gastric emptying and intestinal transit as measured by Evans blue. 1400W completely reversed the endotoxin-induced delay in gastric emptying, while L-NAME did not have these beneficial effects. On the contrary, even in control mice, L-NAME delayed gastric emptying. Dexamethasone, DMSO, and ODQ mimicked the effect of 1400W on endotoxin-induced delay in gastric emptying. The endotoxin-induced delay in transit was significantly improved only by 1400W. None of the drugs reversed the hypothermia. In LPS mice treated with L-NAME, the behavior scale increased even further, while it decreased after treatment with 1400W. In conclusion, selective inhibition of iNOS reverses the endotoxin-induced delay in gastric emptying and transit and improves general well being. The pathway used by NO, derived from iNOS, may involve inhibition of guanylyl cyclase or radical scavenging.