Pharmacological studies on EB-382, a new non-steroidal antiinflammatory agents: mode of action of the analgesic effects

The analgesic mechanism of (+/-)-2-[p-[(2-methylallyl)amino]phenyl]propionic acid (EB-382), a new non-steroidal antiinflammatory agent, was studied. EB-382 exerted a potent analgesic effect on yeast-induced hyperalgesia in rats and bradykinin-induced writhing in mice, and its potency was superior to that of ibuprofen. EB-382 had a comparatively weak inhibitory effect on the prostaglandin E2 production from arachidonic acid in sheep seminal vesicle microsomal fraction in vitro. EB-382 exhibited a dose-dependent inhibitory effect on the phospholipase A2 activity in 3T3 mouse fibroblast cells with a different mechanism from steroidal agents, although indomethacin and ibuprofen did not reveal any significant inhibition. EB-382 did not affect the bradykinin-induced contraction of isolated rat uterus. Intracisternal injection of EB-382 did not affect the acetic acid-induced writhing response in mice. From these results, it is suggested that the analgesic effect of EB-382 in inflammation is exerted through its direct peripheral action, and inhibition of prostaglandin biosynthesis via phospholipase A2, rather than cyclooxygenase.