Regulation of pancreatic secretion by vagal nerve during short-term duct occlusion in conscious rats

The basal exocrine secretion of the pancreas is maintained at a constant le vel in conscious rats. We examined the changes in basal secretion with resp ect to the effect of various time periods of pancreatic duct occlusion (PDL ). Male Wistar rats were prepared with cannulae that separately drained bil e and pancreatic juice as well as with a duodenal cannula. Rats were placed in restraint cages, and experiments were conducted without anesthesia 4 da ys after the operation. Cholecystokinin (CCK) release was artificially prev ented by the continuous infusion of bile with trypsin into the duodenal lum en throughout the experimental period to avoid the modification of pancreat ic response by CCK. After 2-h basal collection, a pancreatic secretion was interrupted for 0.5-4 h, and then the collection of pancreatic juice was in itiated again for an additional 2-4.5 h. The pancreatic secretion after the reopening of the 0.5- to 3-h PDL was comparable to basal secretion levels. However, protein secretion was significantly inhibited after the removal o f 4-h PDL. Both vagotomy and capsaicin treatment abolished this inhibition, and the protein secretion after 1-h PDL in vagotomized rats increased 1.5- fold high compared with the basal value. These observations indicate that p rotein secretion was ceased during PDL via vagal nerve, and this may be a s elf-protective mechanism.