Downregulation of nNOS and synthesis of PGs associated with endotoxin-induced delay in gastric emptying

A single intraperitoneal injection of endotoxin (40 mug/kg) significantly delayed gastric emptying of a solid nutrient meal. Blockade of nitric oxide synthase (NOS) with 30 mg/kg ip N-G-nitro-L-arginine methyl ester or 20 mg/kg ip 7-nitroindazole [neuronal NOS (nNOS) inhibitor] significantly delayed gastric emptying in control animals but failed to modify gastric emptying in endotoxin-treated rats. Administration of 2.5, 5, and 10 mg/kg ip N-6-iminoethyl-L-lysine [inducible NOS (iNOS) inhibitor] had no effect in either experimental group. Indomethacin (5 mg/kg sc), NS-398 (cyclooxygenase-2 inhibitor; 10 mg/kg ip), and dexamethasone (10 mg/kg se) but not quinacrine (20 mg/kg ip) significantly prevented delay in gastric emptying induced by endotoxin but failed to modify gastric emptying in vehicle-treated animals. Ca2+-dependent NOS activity in the antrum. pylorus of the stomach was diminished by endotoxin, whereas Ca2+-independent NOS activity was not changed. In addition, decreased nNOS mRNA and protein were observed in the antrum. pylorus of endotoxin-treated rats. Our results suggest that downregulation of nNOS in the antrum. pylorus of the stomach and synthesis of prostaglandins mediate the delay in gastric emptying of a solid nutrient meal induced by endotoxin.