Possible involvement of 5-HT2 receptor activation in aggravation of diet-induced acute pancreatitis in mice.

Acute pancreatitis was induced in mice by feeding with a choline-deficient ethionine-supplemented diet. All the mice developed acute pancreatitis, and approximately 80% of them died within 4 days. Stereomicroscopic and light microscopic examinations revealed that pancreatic necrosis and circulatory disturbance that were not apparent on day 1 were increased markedly on days 2 and 3. Serum levels of pancreatic enzymes were normal or reduced on day 1 but then increased to peak on day 3. Plasma 5-hydroxyindoleacetic acid levels, which may indicate serotonin release, were significantly increased on days 1 through 3. Pretreatment with D, L-p-chlorophenylalanine methylester hydrochloride (200-400 mg/kg) significantly attenuated the mortality of the mice with pancreatitis. Dose-dependent attenuation was also obtained with ketaserin (0. 01-10 mg/kg), cyproheptadine (0.01-10 mg/kg), pindolol (0.1-100 mg/kg) and NAN-190 (0.1-100 mg/kg), but not with 0.01 to 10 mg/kg of ICS205-930 or M-840, and the activities were significantly correlated with the binding affinities for serotonin2 receptor on the rat cerebral cortex. In addition, ketanserin or cyproheptadine attenuated the morphologic changes in the choline-deficient ethionine-supplemented diet mice at a dose (3.2 mg/kg) that hardly affected the serum enzyme levels. We propose that serotonin2 receptor activation plays an important role in the aggravation of diet-induced acute pancreatitis.