The effects of divalent ions on morphine analgesia and abstinence syndrome in morphine-tolerant and -dependent mice.

Intracerebral administration of copper sulfate potentiated morphine analgesia in morphine-tolerant and -dependent mice, but copper failed to affect other abstinence signs. When abstinence was precipitated with a partial antagonist, nalorphine, stereotyped jumping was not inhibited by either calcium or copper. These modifications of narcotic effects by copper were produced without alterations in the brain disposition of morphine. Total radioactivity in the brain following radioactive naloxone administration was also not altered.