The Effect of 5-Hydroxytryptamine Type 3 Receptor Antagonist on the Motor Activity of the Sphincter of Oddi

Ryu, Ho Sang; Kim, Chang Duck; Jeen, Yoon Tae; Hyum, Jin Hai

Abstract

BACKGROUND AND AIMS: The sphincter of Oddi motor activity is modulated by multifactorial and various neural and hormonal factors. However, it has not been studied whether 5-HT3 receptor antagonist modulate the sphincter of Oddi motor activity. The aim of this study was to confirm the presence of 5-HT on the sphincter of Oddi and to investigate the role of 5-HT3 receptor antagonist in the regulation of motor activity of the sphincter of Oddi in human using ERCP manometry.
METHODS
The motor activity of sphincter of Oddi was examined using ERCP manometry before and after intravenous bolus injection of a selective 5-HT3 receptor antagonist (Ondansetron), 8 mg, in 30 study subjects. To confirm the presence of 5-HT in sphincter of Oddi, immunohistochemical stain was done using resected specimen of ampulla of Vater.
RESULTS
On immunohistochemical staining, we confirm the expression of 5-HT in the normal duodenal mucosa (16 cells/HPF). Ampullary mucosa showed weakly positive stain for 5-HT using anti 5-HT (1.4 cell/HPF). Basal pressure of the sphincter of Oddi was significantly reduced by injection of ondansetron from 10.7+/-0.8 to 8.8+/-0.7 mmHg. Amplitude of phasic contraction was also significantly reduced from 82.9+/-10.9 to 65.4+/-10.5 mmHg. Although frequency of phasic contraction was slightly reduced from 3.1+/-0.6 to 2.5+/-0.4/min, it was not statistically significant.
CONCLUSIONS
These findings suggest that 5-HT3 receptor antagonist has inhibitory effects on the sphincter of Oddi motor activity.