Cerulein-induced pancreatic polypeptide secretion. Its inhibition by atropine and its possible role in regulating gallbladder relaxation.

Intramuscular administration of cerulein caused an abrupt rise in plasma pancreatic polypeptide (PP) in normal subjects. Pretreatment by atropine tended to lower the basal plasma PP level and significantly blunted the cerulein-induced PP secretion. It appears, therefore, that PP secretion induced by cerulein is under vagal control. In addition, in normal subjects, a gallbladder series first revealed a well-filled gallbladder of normal size and shape, which then contracted most strongly after a cerulein injection at a time corresponding exactly with the peak plasma PP levels produced by the cerulein. Since exogenous PP is known to cause a relaxation of the gallbladder, it is possible that endogenous PP plays an important role in gallbladder motility.