Background: Nitric oxide (NO) is known to play an important role in neurally mediated relaxation of the sphincter of Oddi.
Aim: We investigated whether NO donors, such as nitroglycerin or zwitterionic polyamine/NO, applied into the common bile duct or intravenously, may induce the relaxation of the sphincter of Oddi by producing NO in the anaesthetized dog.
Methods: NO production in the sphincter of Oddi was measured by detecting NO oxidation products (NO2- and NO3-) using micro-dialysis methods.
Results: Zwitterionic polyamine/NO and nitroglycerin applied into the common bile duct induced a marked increase in NO2- but not NO3-, in the sphincter of Oddi. Intravenous infusion of zwitterionic polyamine/NO and nitroglycerin induced little or no increase in NO2- formation. Nitroglycerin infused into either the common bile duct or intravenously administered produced relaxation of the sphincter of Oddi, but zwitterionic polyamine/NO had no effect on the sphincter of Oddi in spite of the increase in NO2- levels.
Conclusions: Locally or systemically applied NO donors induce relaxation of the sphincter of Oddi by producing NO, although their mode of action differs in different analogues.