Opiate analgesia: Evidence for circadian rhythms in mice

Alberto Oliverio, Claudio Castellano, Stefano Puglisi-Allegra

Research output: Contribution to journalArticlepeer-review


The effects of a 12-12 h light-dark (L-D) cycle and of constant light (L-L) on nociceptive thresholds and morphine-induced analgesia were studied in two strains of mice: C57BL/6 and SEC/1Re. Under the L-D condition, a diurnal rhythm was observed in the responsivity of mice to nociceptive stimuli, and in the analgesic effects of morphine. Under the L-L schedule clear patterns of daily rhythmicity were evident in both strains for both nociceptive thresholds and responsivity to morphine. Finally, under the L-L schedule, the overall responsivity to pain and the antinociceptive effects of morphine were clearly increased in comparison to the patterns evident in the L-D condition. The administration of naloxone decreased the nociceptive thresholds, thus indicating an involvement of the endogenous opioid peptides. These phenomena are discussed in terms of the different pacemaker mechanisms involved in the expression of various patterns of daily behavioral and neurochemical rhythmicity in these strains, and of the effects of light in controlling the release of endogenous opioids.

Original languageEnglish
Pages (from-to)265-270
Number of pages6
JournalBrain Research
Issue number2
Publication statusPublished - Oct 14 1982


  • circadian rhythms
  • endogenous opioids
  • mice
  • morphine
  • pacemaker mechanisms
  • pain

ASJC Scopus subject areas

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


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