Post-natal morphine differentially affects opiate and stress analgesia in adult rats

Dulmanie Arjune, Richard J. Bodnar

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Alterations in nociceptive reactivity, opiate receptor binding, and other behavioral responses occur in rats exposed to morphine either in utero or post-natally. The present study examined whether post-natal morphine (0, 1 or 20 μg, days 1-7) altered analgesia on the tail-flick and jump tests induced by nonopioid-mediated continuous cold-water swims (CCWS), opioid-mediated intermittent cold-water swims (ICWS) or morphine (2.5 and 5.0 mg/kg, SC) in adult male and female rats. Changes in body weight, developmental sings (e.g., eye opening), basal pain thresholds, and both CCWS and ICWS hypothermia were also assessed. Previously-reported gender differences occurred for all forms of analgesia in control rats. Post-natal morphine treatment transiently increased ICWS analgesia and hypothermia, and transiently decreased CCWS analgesia and hypothermia, suggesting that these effects were not specific to pain inhibition. Post-natal morphine treatment significantly increased the magnitude of morphine analgesia on both tests in females, and significantly decreased the magnitude of morphine analgesia on both tests in males, thereby acting to vitiate the observed gender differences in morphine analgesia. Such effects could not be explained by concomitant changes in other measures. These data indicate that post-natal morphine treatment exerts highly selective effects upon specific analgesic responses which are gender sensitive.

Original languageEnglish
Pages (from-to)512-517
Number of pages6
JournalPsychopharmacology
Volume98
Issue number4
DOIs
StatePublished - Aug 1989
Externally publishedYes

Keywords

  • Opiate and stress analgesia
  • Post-natal morphine

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