Aim: To study the antagonism of sincalide to the effect of morphine and its mechanism.
Methods: The electrophysiologic and mechanic activities of rat jejunum in vitro were recorded.
Results: Acetylcholine (ACh, 150 nmol.L-1) increased the spike potential amplitude (SPA) and the number (SPN) of rat jejunum in vitro, followed by an increase of jejunal contraction amplitudes (CA), showing a positive correlation. Morphine 330 nmol.L-1 inhibited the potentiation of ACh, showing a negative correlation. Sincalide 0.7 nmol.L-1 antagonized the effects of morphine, i.e., the SPA and SPN were increased again, followed by an increase of CA. CCK-A receptor antagonist devazepide (10 nmol.L-1) reversed the antagonism of sincalide to the effect of morphine.
Conclusion: Sincalide antagonized the effect of morphine which inhibited the potentiation of ACh on jejunal activities in vitro. The antagonistic effect of sincalide on morphine was mainly mediated by CCK-A receptor.