The influence of dopamine receptor agonists and an antagonist on acute pancreatitis in rats.

The influence of the dopamine receptor-stimulating agent, bromocriptine, the dopamine-releasing drug, amantadine, and the dopamine antagonist, domperidone, on acute pancreatitis was studied in rats. Acute pancreatitis was induced by ligation of the bile duct at its point of entry into the duodenum. Each drug was applied intraperitoneally 1 h before induction of acute pancreatitis and all the surviving animals were killed 24 h thereafter. The control, saline-pretreated animals exhibited the mortality rate, macroscopical and histological changes, as well as increase of serum amylase levels that were consistent with acute pancreatitis. Domperidone induced a large increase in serum amylase which was significantly reduced by the simultaneous administration of bromocriptine. However, both bromocriptine and amantadine, when given separately did not prevent the increase of serum amylase levels to the control levels. Statistical analysis showed that the difference between the mortality rate in the control and treated groups did not reach the level of significance probably due to the rather limited number of animals used. On the other hand, application of bromocriptine as well as amantadine successfully reduced the onset of acute pancreatitis whereas domperidone, a rather specific peripheral dopamine receptor blocker, had the opposite effect. Both bromocriptine and amantadine significantly reduced the mortality rate from acute pancreatitis in domperidone-pretreated rats. Since the aggravating effect of domperidone was successfully reduced by simultaneous application of bromocriptine, we think that these effects are mediated by peripheral dopamine receptors. However, the mechanisms whereby dopamine receptor-stimulating and dopamine-releasing drugs produce their beneficial effects remain to be elucidated.