UI - 000044

AU - Kayser V

AU - Besson JM

AU - Guilbaud G

TI - Analgesia produced by low doses of the opiate antagonist naloxone in arthritic rats is reduced in morphine-tolerant animals

AB - In a model of experimental chronic pain (adjuvant-induced arthritic rats), low doses of the opiate

antagonist naloxone produced a profound analgesia. Maximum analgesia was seen with 3 micrograms/kg

(i.v.). In contrast, hyperalgesia was obtained with much higher doses (1-3 mg/kg, i.v.). The hyperalgesic

effects were not affected in arthritic animals rendered tolerant to morphine, but the paradoxical analgesic

effects were significantly reduced. This decrease suggests that naloxone analgesia involves interaction with

opiate receptors and that the operation of endorphinergic systems differs in normal animals and animals

which experience persistent pain

SO - Brain Research 1986;371:37-41