In the present study the effect of atropine on feedback regulation of pancreatic function was investigated in male rats. Orogastric tube feeding of a single dose of the protease inhibitor camostate (100 mg) caused a 6-fold increase in plasma CCK. This was accompanied by a 50% decrease in pancreatic enzyme content for up to 6 h. The effect of i.v. infusion of atropine (100 micrograms.kg-1.h-1) was studied 60 and 180 min after camostate feeding. Atropine completely abolished the decrease in enzyme content 180 min after camostate feeding. The stimulated CCK plasma levels were significantly lowered by the infusion of atropine 60 min, but not 180 min, after feeding of camostate. It is discussed that a cholinergic pathway mediates CCK release in the early phase of feedback regulation of pancreatic function.