Involvement of nitric oxide in 5-HT 3 receptor agonist-induced fluid accumulation in jejunum and colon of anesthetized rats

Objectives : The aim of the present study was to investigate the involvement of nitric oxide in 5-HT₃ receptor agonist-induced fluid accumulation in jejunum and colon of anesthetized rats.
Materials and Methods : Fluid movement in jejunum and colon were determined simultaneously in the same rat, by modifying the Beubler method. Nv-nitro-L-arginine (L-NNA, 20 mg/kg, s.c) alone and in combination with L-arginine (L-Arg, 150 mg/kg s.c) or D-arginine (D-Arg, 150 mg/kg, s.c) were administered 30 min before administration of 1-PBG (18.5 μg/kg, i.v).
Results : Intravenous administration of 1-phenylbiguanide (1-PBG) induced a net secretion of fluid in both jejunum and colon. 1-PBG had a more prominent secretory effect in the colon, causing a three-fold increase in volume of fluid secreted/g of colon than in the jejunum. Pretreatment with (L-NNA) prevented the 1-PBG-induced fluid accumulation in both jejunum and colon. The inhibitory effect of L-NNA on 1-PBG-induced fluid accumulation was reversed by L-Arg but not by D-Arg.
Conclusion : These results provide evidence that nitric oxide plays an important role in 5-HT₃ receptor agonist-induced fluid accumulation in jejunum and colon of anesthetized rats.