[Acetylcholine potentiation of the serotonin-induced contractile reaction of the cat pyloric sphincter].

Isolated feline gastroduodenal junction was incubated in oxygenated Krebs solution maintained at 37 degrees C. Three types of spontaneous contractile activity were observed in the experiments. Acetylcholine and serotonin, 1.10(-11)-1.10(-5) mol/l, elicited contractile response of the pyloric sphincter consisting of tonic and rhythmic components. Acetylcholine, 1.10(-10)-1.10(-11) nmol/l, while being unable to induce contractile activity of the preparation, potentiated the contractile response of the pyloric sphincter elicited by serotonin.