AIM: To examine the effects of pancreatic rest, stimulation and rest/stimulation on the natural course of recovery after acute pancreatitis. METHODS: Acute hemorrhagic pancreatitis(AP) was induced in male rats by intraductal infusion of 40 μl/100 g body weight of 3% sodium taurocholate. All rats took food ad libitum. At 24 h after induction of AP, rats were divided into four groups: control(AP-C), pancreas rest(AP-R), stimulation(AP-S), and rest/stimulation(AP-R/S). Rats in the AP-C, AP-R and AP-S groups received oral administration of 2 ml/kg body weight saline, cholecystokinin(CCK)-1 receptor antagonist, and endogenous CCK release stimulant, respectively, twice daily for 10 d, while those in the AP-R/S group received twice daily CCK-1 receptor antagonist for the first 5 d followed by twice daily CCK release stimulant for 5 d. Rats without any treatment were used as control group(Control). Biochemical andhistological changes in the pancreas, and secretory function were evaluated on day 12 at 24 h after the last treatment. RESULTS: Feeding ad libitum(AP-C) delayed biochemical, histological and functional recovery from AP. In AP-C rats, bombesin-stimulated pancreatic secretory function and HOMA-β-cell score were significantly lower than those in other groups of rats. In AP-R rats, protein per DNA ratio and pancreatic exocrine secretory function were significantly low compared with those in Control rats. In AP-S and AP-R/S rats, the above parameters recovered to the Control levels. Bombesinstimulated pancreatic exocrine response in AP-R/S rats was higher than in AP-S rats and almost returned to control levels. In the pancreas of AP-C rats, destruction of pancreatic acini, marked infiltration of inflammatory cells, and strong expression of α-smooth muscle actin, tumor necrosis factor-α and interleukin-1β were seen. Pancreatic rest reversed these histological alterations, but not atrophy of pancreatic acini and mild infiltration of inflammatory cells. In AP-S and AP-R/S rats, the pancreas showed almost normal architecture. CONCLUSION: The favorable treatment strategy for AP is to keep the pancreas at rest during an early stage followed by pancreatic stimulation by promoting endogenous CCK release. METHODS: Acute hemorrhagic pancreatitis (AP) was induced in male rats by intraductal infusion of 40 μl / 100 g body weight of At 24 h after induction of AP, the rats were divided into four groups: control (AP-C), pancreas rest (AP-R), stimulation (AP-S), and Rest / stimulation (AP-R / S). Rats in the AP-C, AP-R and AP-S groups received oral administration of 2 ml / kg body weight saline, cholecystokinin (CCK) -1 receptor antagonist, and endogenous CCK release stimulant, respectively, twice daily for 10 d, while those in the AP-R / S group received twice daily CCK-1 receptor antagonist for the first 5 d followed by twice daily CCK release stimulant for 5 d. Rats without any treatment were used as control group (Control). Biochemical andhistological changes in the pancreas, and secretory function were as on d ay 12 at 24 h after the last treatment. RESULTS: Feeding ad libitum (AP-C) delayed biochemical, histological and functional recovery from AP. In AP-C rats, bombesin-stimulated pancreatic secretory function and HOMA-β-cell score were significantly lower than those in other groups of rats. In AP-R rats, protein per DNA ratio and pancreatic exocrine secretory function were significantly lower compared with those in Control rats. In AP-S and AP-R / S rats, the above parameters recovered to the Control levels. Bombesinstimulated pancreatic exocrine response in AP-R / S rats was higher than in AP-S rats and almost returned to control levels. In the pancreas of AP-C rats, destruction of pancreatic acini, marked infiltration of inflammatory cells, and strong expression of α-smooth muscle actin, tumor necrosis factor-α and interleukin-1β were seen. Pancreatic-derived and histological alterations, but not atrophy of pancreatic acini and mild infiltration of inflammatory cells. In AP-S and A P-R / Srats, the pancreas showed almost normal architecture. CONCLUSION: The favorable treatment strategy for AP is to keep the pancreas at rest during an early stage followed by pancreatic stimulation by promoting endogenous CCK release.