Somatic electrical nerve stimulation regulates the motility of sphincter of Oddi in rabbits and cats: evidence for a somatovisceral reflex mediated by cholecystokinin.

Cholecystokinin (CCK) plays an important role in regulating the biliary motility in herbivorous and carnivorous animals. Little is known about how the motility of the sphincter of Oddi (SO) is regulated through a somatic stimulation. It was our aim to test the hypothesis that somatic electrical nerve stimulation (SENS) affects SO motility in animals with different types of SO through CCK-related mechanisms. The activity of SO in anesthetized rabbits and cats was measured by using a continuously perfused open-tip manometric method. SENS was brought about by applying an electric current (2/15 Hz alternatively, 20 min) to two needles positioned near spinal nerves in the 6th and 7th intercostal space in the right midclavicular line. The SO motility before and X min after the start of SENS, designated as pre-SENS and SENS-X respectively, were recorded and saved in a computer equipped with off-line analysis software. The SO activity in rabbits, in terms of phasic contraction pressure and duration of summation peak during SENS were significantly higher than that before SENS. The phasic contraction pressure of pre-SENS, SENS-10, and SENS-16 were 6.83 +/- 0.39 mm Hg, 9.23 +/- 0.83 mm Hg and 10.46 +/- 0.81 mm Hg, respectively (P < 0.03, N = 13). The duration of summation peak in pre-SENS, SENS-10, and SENS-16 were 7.26 +/- 0.41 sec, 10.22 +/- 0.46 sec, and 13.49 +/- 2.31 sec, respectively (P < 0.05, N = 13). The SENS-induced SO hyperactivity was not inhibited by pretreatment with atropine, propranolol, phentolamine, or naloxone, but was blocked by pretreatment with the CCK receptor antagonist, proglumide, and by injection of anti-CCK-8 antibody during SENS in a dose-dependent manner. In contrast, SENS induced an inhibitory SO response in cats. However, in both circumstances, an obvious elevation of plasma CCK level determined by radioimmunoassay was noted after SENS. We conclude that SENS causes secretion of CCK, which in turn affects biliary tract motility in animals with different types of SO. This provides an easily applicable method for those patients who have hyperactive SO function.