A portion of duodenum laid pancreatic duct opening were perfused continuously with physiological saline under urethane anesthesia in rats. The pancreatic amylase secretory response to caerulein was studied with autonomic blockers, such as phenoxybenzamine, dibenamine, phentolamine, hexamethonium, propranolol, atropine, and cyproheptadine. The pancreatic amylase output to caerulein, 7.5ng/kg i.v., was markedly increased and the value was approximately three times greater than control. The caerulein-stimulated pancreatic amylase secretion was significantly decreased by i.v. phenoxybenzamine and propranolol treatment, but not by phentolamine or dibenamine. Secretory response of pancreatic amylase to caerulein was not affected by i.v. atropine, hexamethonium or cyproheptadine. These result lead to the conclusion that phenoxybenzamine may inherently inhibit the secretory response of pancreatic amylase to caerulein, and this effect was not related with α-adrenergic receptor blocking action.