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A single intraperitoneal injection of endotoxin (40 [micro]g/kg) significantly delayed gastric emptying of a solid nutrient meal. Blockade of nitric oxide synthase (NOS) with 30 mg/kg ip [N.sup.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.sup.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 sc) 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. [Ca.sup.2+]-dependent NOS activity in the antrum pylorus of the stomach was diminished by endotoxin, whereas [Ca.sup.2+]-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. nitric oxide; prostaglandins; antrum pylorus; nutrient meals