Naloxone-induced analgesia: involvement of kappa-opiate receptors

Pharmacol Biochem Behav. 1993 Sep;46(1):145-8. doi: 10.1016/0091-3057(93)90331-m.

Abstract

Rats treated with an acute high dose (30 mg/kg) or 4 days with a lower dose (5 mg/kg) of naloxone or naltrexone show an analgesic response at the hot-plate test. This paradoxical analgesic effect of the two mu-opiate receptor antagonists is blocked by the kappa opiate receptor antagonist MR 1452, and is modulated by the kappa opiate receptor agonist U 50-488. Our results suggest that kappa opiate receptors are involved in naloxone-induced analgesia and are consistent with a high degree of plasticity of the opiatergic system.

MeSH terms

  • 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer
  • Analgesia*
  • Analgesics / pharmacology
  • Animals
  • Benzomorphans / pharmacology
  • Male
  • Naloxone / pharmacology*
  • Naltrexone / pharmacology
  • Narcotic Antagonists / pharmacology
  • Pain Threshold / drug effects
  • Pyrrolidines / pharmacology
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Opioid, kappa / drug effects*
  • Receptors, Opioid, mu / drug effects

Substances

  • Analgesics
  • Benzomorphans
  • Narcotic Antagonists
  • Pyrrolidines
  • Receptors, Opioid, kappa
  • Receptors, Opioid, mu
  • Naloxone
  • Naltrexone
  • 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer
  • Mr 1452