Acute and chronic morphine alters formalin pain in neonatal rats

https://doi.org/10.1016/j.neulet.2006.02.039Get rights and content

Abstract

The present study tested the hypothesis that morphine exposure during the human developmental equivalent of the third trimester would alter inflammatory pain. This study examined whether acute or continuous opioid exposure in the neonatal rat alters formalin-induced nociception after 4 days of abstinence. Rats were exposed to a single acute administration of morphine on postnatal day 7 or 72 h of opioid infusion from postnatal days 5–7 via osmotic pump. When challenged with intraplantar formalin on postnatal day 11, rats exposed to acute or chronic morphine had increased phase II pain-associated behaviors. These findings suggest that neonatal morphine exposure may have unintended consequences on inflammatory pain.

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Cited by (11)

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  • Morphine exposure during early life alters thermal and mechanical thresholds in rats

    2017, International Journal of Developmental Neuroscience
    Citation Excerpt :

    Furthermore, it has been demonstrated that neonatal manipulations are capable of displaying long-lasting alterations; for example, neonatal stress exaggerates adult arousal, whereas neonatal morphine treatment reduces adult arousal (Boasen et al., 2009). Besides, short-term effects can be observed after neonatal morphine treatment, where rats acutely or chronically exposed to morphine displayed increased phase II pain-associated behaviors in formalin test at P11 (Zissen et al., 2006). Moreover, hippocampal structure changes were observed after recurrent morphine administration during brain development (Traudt et al., 2012).

  • Behavioral effects of perinatal opioid exposure

    2014, Life Sciences
    Citation Excerpt :

    Intraplantar formalin-induced pain reactions were reduced by acute morphine treatment in neonates (Abbott and Guy, 1995). However, when the postnatal morphine administration was followed by 4 days of abstinence, the pain reaction increased significantly (Zissen et al., 2006). Similarly, antinociceptive tolerance to morphine administration developed, as measured by a hot plate test (Bajic et al., 2013).

  • Morphine exposure in early life increases nociceptive behavior in a rat formalin tonic pain model in adult life

    2011, Brain Research
    Citation Excerpt :

    Thus, the increase in formalin-induced nociceptive behavior observed in this study suggests a central hyperexcitability of the ascending second-order dorsal horn neurons induced by previous sustained exposure to morphine, and this is a long-term effect. Our results agree with those of Zissen et al. (2006, 2007), who have demonstrated that while infant rats (P5 to P8) are more sensitive to the long-term changes in formalin-induced pain and mechanical thresholds following continuous exposure to morphine, when compared to young rats (P19 to P21), they are also better able to compensate for changes in mechanical thresholds following intermittent administration of morphine, given twice a day for 3 days. It is possible that short bouts of morphine withdrawal-induced excitation may off-set morphine-induced inhibition in infants, but not in young rats, and thus, may better maintain the balance of activity and inactivity during this crucial developmental phase.

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    2009, International Journal of Developmental Neuroscience
    Citation Excerpt :

    These behavioral reflexes are considered the most sensitive and specific measures of pain (Guy and Abbott, 1992). It has been shown that the opioid analgesia attenuates these specific pain behaviors in 2-week-old rats (Zissen et al., 2006). In accordance, the maturation of C-fiber input to the spinal cord is completed around the second postnatal week (Jenning and Fitzgerald, 1998).

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