Kappa opioid receptors in rat spinal cord vary across the estrous cycle

Peter C. Chang, Sue A. Aicher, Carrie T. Drake

Research output: Contribution to journalArticlepeer-review

41 Scopus citations


Kappa opioid receptors (KORs) were immunocytochemically localized in the lumbosacral spinal cord of female rats in different stages of the estrous cycle to examine the influence of hormonal status on receptor density. KOR labeling was primarily in fine processes and a few neuronal cell bodies in the superficial dorsal horn and the dorsolateral funiculus. Quantitative light microscopic densitometry of the superficial dorsal horn revealed that rats in diestrus had significantly lower KOR densities than those in proestrus or estrus. This suggests that female reproductive hormones regulate spinal KOR levels, which may contribute to variations in analgesic effectiveness of KOR agonists across the estrous cycle.

Original languageEnglish (US)
Pages (from-to)168-172
Number of pages5
JournalBrain research
Issue number1
StatePublished - Apr 7 2000
Externally publishedYes


  • Female
  • Gender
  • Pain
  • Sex difference

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology


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