Lithium attenuates pain-related behavior in a rat model of neuropathic pain: Possible involvement of opioid system

► Lithium reduces hyperalgesia and allodynia in rat model of neuropathic pain. ► Naloxone had no effect on behavioral tests of neuropathic pain. ► Naloxone reverses the effect of lithium in reduction of neuropathic pain. ► Our result suggests the possible involvement of opioid system in this effect.