Effect of PAF-acether antagonists on active anaphylactic mouse paw edema

A new model of active anaphylactic reaction in mice was developed. The edematogenic reaction appeared 5 min after the intraplantar injection of ovalbumin, peaked at 30 min after the antigenic challenge, and decreased thereafter. Using the non-steroidal, anti-inflammatory agents indomethacin and aspirin, we found that cyclooxygenase products do not participate in the reaction. In contrast, vasoactive amines appear to be involved, because meclizine and methysergide reduced the edema. Dexamethasone, BW755C, LY 171883 and WEB 2170 effectively interfered with the edematogenic reaction, which suggests that lipid mediators such as leukotrienes and PAF play a role in the active anaphylactic response.