AIM To investigate the effects of riluzole(2 amino 6 trifluoromethoxy benzothiazole) on opioid actions in mice. METHODS
The effects of riluzole on pain threshold and morphine analgesia were observed in acetic acid writhing test, 55℃ hot plate test and heat radiation tail flick assay. The effects of riluzole on acute and chronic morphine tolerance and physical
dependence in mice were observed. RESULTS In mouse acetic acid writhing test, 55℃ hot plate test and heat radiation tail flick assay, riluzole(2.5 to 10 mg·kg -1 , sc) administrated 20 min before morphine administration enhanced morphine analgesia in a dose
dependent manner. However, riluzole(10 mg·kg -1 ) alone had no analgesic effects. Riluzole(2.5 to 10 mg·kg -1 ) prevented the development of tolerance to morphine in a dose dependent manner in acute and chronic tolerance models. In substance dependence experiment, withdrawal jumps and loss in body weight precipitated by naloxone in morphine dependent mice were inhibited by co administration of riluzole(2.5 to 10 mg·kg -1 , sc) with morphine in a dose dependent manner. CONCLUSION Riluzole is not able to elevate the pain threshold, but enhances morphine analgesia, inhibits tolerance to and dependence on morphine in mice.