EFFECTS OF VARIOUS ANALGESIC AND ANTIINFLAMMATORY DRUGS ON ENDOTOXIN-INDUCED HYPERALGESIA IN RATS AND MICE

A new model of endotoxin (ET)-induced hyperalgesia has been used to te st the effects of four classes of drugs in rats and mice. Hyperalgesia was assessed by paw pressure (PP), hot plate (HP) and tail flick (TF) tests. Each drug was injected intraperitoneally 24 and 12h before ET injection and just before each pain test at 3, 6, 9 and 24 h after ET injection. At the dosages used, acetaminophen and dexamethasone were t he most effective in reducing PP hyperalgesia and least effective on T F hyperalgesia, while indometacin and morphine produced their main eff ect on TF hyperalgesia. The four drugs were about equally effective in reversing HP hyperalgesia. We conclude that ET hyperalgesia is mediat ed by both prostaglandin-sensitive and prostaglandin-independent mecha nisms.