Ethanol inhibits the motility of rabbit sphincter of Oddi in vitro.

Aim: The role of the sphincter of Oddi (SO) in ethanol (ETOH)-induced pancreatitis is controversial. Our aim was to characterise the effect of ETOH on basal and stimulated SO motility.

Methods: SOs removed from white rabbits were placed in an organ bath (Krebs solution, pH7.4, 37 degrees). The effects of 2 mL/L, 4 mL/L, 6 mL/L and 8 mL/L of ETOH on the contractile responses of the sphincter were determined. SOs were stimulated with either 0.1 mumol/L carbachol, 1 mumol/L erythromycin or 0.1 mumol/L cholecystokinin (CCK).

Results: ETOH at a dose of 4 mL/L significantly decreased the baseline contractile amplitude from 11.98+/-0.05 mN to 11.19+/-0.07 mN. However, no significant changes in the contractile frequency were observed. ETOH (0.6%) significantly decreased both the baseline amplitude and the frequency compared to the control group (10.50+/-0.01 mN, 12.13+/-0.10 mN and 3.53+/-0.13 c/min, 5.5+/-0.13 cycles(c)/min, respectively). Moreover, 0.8% of ETOH resulted in complete relaxation of the SO. Carbachol (0.1 micromol/L) or erythromycin (1 micromol/L) stimulated the baseline amplitudes (by 82% and 75%, respectively) and the contractile frequencies (by 150% and 106%, respectively). In the carbachol or erythromycin-stimulated groups 2-6 mL/L of ETOH significantly inhibited both the amplitude and the frequency. Interestingly, a 4-5 min administration of 0.6% ETOH suddenly and completely relaxed the SO. CCK (0.1 micromol/L) stimulated the baseline amplitude from 12.37+/-0.05 mN to 27.40+/-1.82 mN within 1.60+/-0.24 min. After this peak, the amplitude decreased to 17.17+/-0.22 mN and remained constant during the experiment. The frequency peaked at 12.8+/-0.2 c/min, after which the constant frequency was 9.43+/-0.24 c/min throughout the rest of the experiment. ETOH at a dose of 4 mL/L significantly decreased the amplitude from 16.13+/-0.23 mN to 14.93+/-0.19 mN. However, no significant changes in the contractile frequency were observed. ETOH at a dose of 6 mL/L inhibited both the amplitudes and the frequencies in the CCK-stimulated group, while 8 mL/L of ETOH completely relaxed the SO.

Conclusion: ETOH strongly inhibits the basal, carbachol, erythromycin, and CCK-stimulated rabbit SO motility. Therefore, it is possible that during alcohol-intake the relaxed SO opens the way for pancreatic fluid to flow out into the duodenum in rabbits. This relaxation of the SO may protect the pancreas against alcohol-induced damage.