Effect of prostaglandins E1, E2, and F2 alpha on the electric activity of the sphincter of Oddi in living rabbit.

The effect of prostaglandins (PGs), i.e. PGE1, PGE2 and PGF2 alpha (0.5-32 micrograms/kg), on the electrical activity of the rabbit sphincter of Oddi was studied in vivo. PGs were injected intravenously as a bolus and electrical activity of the sphincter and the duodenum was recorded before and during 15 min after the injection. Variations in biliary pressure were also studied at the same time. PGE1 strongly decreased the activity of the sphincter and biliary pressure which were both increased by PGF2 alpha. Both PGE1 and PGF2 alpha showed a dose-response curve of Michaelis-Menten type. Unexpectedly PGE2 increased at first then decreased electrical activity but not significantly. These effects appeared very early after intravenous injection and were evident with low doses.