Asperlicin (ASP), a new, nonpeptidal cholecystokinin (CCK) receptor antagonist isolated from the fungus Aspergillus alliaceus, has an affinity that is 300-400 times greater than that of proglumide for gallbladder, ileal, and pancreatic CCK receptors. The long in vivo half-life and high selectivity for peripheral CCK receptors make ASP suitable for investigations on the physiological and pharmacological actions of CCK. Endogenous CCK has been postulated to participate in the pathogenesis of acute hemorrhagic pancreatitis (AHP) in rats and mice. We examined the effects of ASP in rats on the early course (6 h) of AHP induced by a retrograde infusion of sodium taurocholate (NaTC) into the common bile-pancreatic duct. An i.v. bolus injection of ASP (either 10 mg/kg or 30 mg/kg) in dimethyl sulfoxide (DMSO) given 1 h prior to AHP induction failed to significantly alter pancreas weights, serum amylase concentrations, or pancreatic histopathology when compared with AHP control rats treated with vehicle alone. However, rats given 2 i.p. injections of ASP (either 20 mg/kg/injection or 40 mg/kg/injection) in DMSO: olive oil 1 h before and 2 h after induction of AHP exhibited significantly reduced serum amylase concentrations. Additionally, rats given the high dose i.p. injections of ASP also had significantly reduced pancreas weights and less severe pancreas histopathology compared with AHP control animals. These data indicate that endogenous CCK participates in the pathogenesis of NaTC-induced AHP in the rat.