METOCLOPRAMIDE ENHANCES BETHANECHOL-INDUCED PANCREATIC EXOCRINE SECRETION OF THE DOG

1. The effects of metoclopramide on pancreatic exocrine secretion were investigated in the pentobarbitone-anaesthetized dog. All drugs were injected into the femoral vein. 2. Metoclopramide (10–1000 μg/kg) did not change the resting rate of pancreatic secretion. 3. Pancreatic secretion, induced by bethanechol (3 μg/kg), was dose-dependently enhanced by simultaneous injections of metoclopramide (10 and 30 μg/kg), but the protein and bicarbonate concentrations of the pancreatic juice were not affected. Secretions induced by secretin (0.1 units/kg) and dopamine (3 μg/kg) were not modified by metoclopramide at up to 30 μg/kg. 4. A larger dose of metoclopramide (1000 μg/kg) suppressed dopamine-induced secretion to a lesser extent than the same dose of sulpiride. 5. From these results, it is concluded that metoclopramide enhances secretory responses to cholinergic stimulations by peripherally sensitizing the muscarinic receptor-mediated exocrine process and this drug is a weaker antagonist of the dopamine D₂ receptors than sulpiride.