Chronic antagonist infusion does not increase morphine antinociception in rat spinal cord.
Chronic spinal infusion of the opiate antagonists naloxone or naltrexone fail to influence the antinociceptive effect of subsequent intrathecal morphine on the hot plate test in rats compared to saline-infused controls. These results contrast the functional supersensitivity to morphine seen after long-term systemic opiate antagonist administration and support the hypothesis that dopaminergic interactions, lacking in the spinal cord, are necessary for antagonist-induced opioid receptor upregulation.
Laboratory of Neurosurgical Research, Mayo Clinic, Rochester, MN 55905.
C W
CW
Stevens
T L
TL
Yaksh
D000818:Animals; D007278:Injections, Spinal; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology*; D009271:Naltrexone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology; D009619:Nociceptors / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D013116:Spinal Cord / Q000187:drug effects*
D009292:Narcotic Antagonists; D009270:Naloxone; D009271:Naltrexone; D009020:Morphine