Inhibitory effects of morphine on some inflammation-related parameters in the goldfish Carassius auratus L.

Acute peritonitis induced in the goldfish by intraperitoneal injection of a sterile Thioglycollate solution shows a typical pattern with intraperitone al exudation of serum proteins followed by influx of leucocytes (mainly het erophils/macrophages) correlated with elevated levels of chemotactic factor s in peritoneal fluid and blood plasma. Supplementation of Thioglycollate w ith morphine (20 mg kg(-1) b.w.) does not affect the leakage of serum prote ins into peritoneum. In contrast, it reduces the number of exudate peritone al leucocytes (among them heterophils/macrophages) to the control level and decreases the level of peritoneal fluid/plasma chemoattractants, both effe cts being reversed by naltrexone pretreatment. Morphine itself acts as a ch emokinetic factor for fish leucocytes as it increases their random movement s. Therefore inhibitory effects of morphine on accumulation of exudate cell s might be explained by inhibition of the production/release of chemotactic factors and/or reduced sensitivity of leucocytes to chemotactic signals. T he effects of morphine on the goldfish peritonitis are in concordance with those described recently in Atlantic salmon and CB6 mice. (C) 2000 Academic Press.