Influence of serotonin, serotonin antagonists, some vasoactive substances and temperature on carrageenin-induced tail thrombosis in rats and mice.

Tail thrombosis (infarction) induced by injection of kappa-carrageenin (0.88 or 1.76 mg/kg i.v.) is increased by i.v. or i.p. serotonin (1-2 mg/kg) but is decreased by cyproheptadine and ketanserin (minimal effective dose less than 1 mg/kg) as well as by preceding serotonin depletion by comp. 48/80 or reserpine. The effect of exogenous serotonin is antagonized by ketanserin and cyproheptadine, respect. In the anaphylactoid reaction induced by dextran, only weak thrombosis increasing effects were seen, apparently, because of vasodilation in this reaction. Application of heat to the tail weakly decreased tail thrombosis, application of cold strikingly increased it. Vasodilating substances (nicotinate, 3-hydroxymethylpyridine, trapidil, dipyridamole, iloprost) as well as the thromboxane antagonist BM 13,177 were without significant effect on tail thrombosis, even if vasodilating substances were applicated in form of ointments on the tail. The participation of endogenous serotonin in carrageenin-induced tail thrombosis has further to be substantiated.