We examined the effects of treatment with cholecystokinin (CCK) octapeptide (CCK-8) and the CCK receptor antagonist loxiglumide on the recovery of exocrine pancreas in post-acute pancreatitic rats. Acute pancreatitis was induced in rats by intravenous infusion of 20 microg/kg/h cerulein for 4 h. At 24 h after the start of cerulein infusion, rats were divided into nine treatment groups: oral administration of saline (control), or oral administration of 10 or 50 mg/kg body weight loxiglumide twice daily for the first 3 days, followed by saline administration (Loxi-1 and Loxi-2), 10 or 50 mg/kg body weight loxiglumide twice daily for 6 days (Loxi-3 and Loxi-4), oral administration of saline or 10 or 50 mg/kg body weight loxiglumide twice daily for the first 3 days, followed by subcutaneous injection of 2.5 microg/kg body weight CCK-8 twice daily for the next 3 days (CCK-1, CCK-2, and CCK-3), and subcutaneous injection of 2.5 microg/kg body weight CCK-8 twice daily for 6 days (CCK-4). Pancreatic wet weight and biochemical changes were evaluated on day 8 at 12 h after the last treatment. Treatment with loxiglumide (Loxi-3 and Loxi-4) or CCK-8 for 6 days (CCK-4) or with a high dose of loxiglumide for the first 3 days (Loxi-2) significantly suppressed the recovery of pancreatic weight and DNA content compared to saline treatment or to the untreated normal control rats. However, when loxiglumide treatment was followed by 3 days of CCK-8 injections (CCK-2 and CCK-3), pancreatic protein and DNA content recovered to levels comparable to or above the control levels. The most remarkable increase in enzyme content was obtained in postpancreatitic rats treated with high-dose loxiglumide for the first 3 days, followed by CCK-8 injection (CCK-3). On the other hand, 6 days of CCK-8 treatment (CCK-4) had no significant influences on pancreatic enzyme contents. These results suggest that the most favorable strategy for the treatment of acute pancreatitis is to give high-dose loxiglumide during the early stage for only a short period, followed by CCK-8 administration.