Effect of endotoxin on opossum oesophageal motor function

Endotoxin induces nitric oxide (NO.) synthase and alters gastrointestinal f unctions. We explored the effect of lipopolysaccharide (LPS) on oesophageal motor function at 6, 12, 24, and 48 h. The effects of inhibiting inducible NO. synthase (iNOS) were studied 12 h after administration of LPS with/wit hout aminoguanidine (AG). Oesophageal manometry was performed and tissue ba th studies were performed with muscle strips from the oesophagus and lower oesophageal sphincter (LOS). Plasma nitrite/nitrate concentrations were det ermined. The amplitudes of peristaltic pressure waves, resting LOS pressure and the percentage LOS relaxations were diminished by LPS. AG attenuated t he decrease in amplitude of oesophageal pressure waves, LOS pressure, and p ercentage relaxation of LOS brought about by LPS. LPS decreased electrical field stimulation (EFS)-induced relaxation of LOS muscle. AG attenuated thi s decrease in LOS relaxation. The off-response of transverse oesophageal mu scle strips was decreased, and AG antagonized this effect. Plasma concentra tions of nitrite/nitrate were increased. The increase in plasma nitrite/nit rate was attenuated by AG. These studies support the hypothesis that endoto xin modulates oesophageal motor function by increasing NO production and su ggest that this results from the induction of iNOS.