Elsevier

The Journal of Pain

Volume 5, Issue 8, October 2004, Pages 420-426
The Journal of Pain

Nociception and antinociception during the first week of life in mice: Sex differences and test dependence

https://doi.org/10.1016/j.jpain.2004.07.002Get rights and content
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Abstract

This study demonstrates that reliable sex differences in nociceptive and antinociceptive mechanisms are present in even very young subjects. Sex differences were observed in mice tested either on the day of birth or 1 week later on basal tail-flick latency and morphine analgesic magnitude. Female mice had longer tail-withdrawal latencies; male mice demonstrated stronger analgesic responses to morphine. In addition, basal pain behavior and analgesic responsiveness differed between day-old and week-old animals on the hot plate, with day-old mice showing enhanced pain behavior and reduced morphine antinociception compared to week-old subjects. These findings further support the competence of pain processing circuitry in even very young subjects and highlight the early development of nociceptive and antinociceptive mechanisms.

Perspective

This study highlights the competence of nociceptive circuitry and the analgesic efficacy of morphine as early as the day of birth in mice, reinforcing the importance of evaluating and treating pain in even the youngest subjects. Sex differences were present, suggesting infant sex as one of several potential factors that predict the experience of procedural or pathological pain and analgesic requirement.

Key words

Neonatal
morphine
mouse
sex differences

Cited by (0)

Supported by a National Science Foundation Research at Undergraduate Institutions grant and a Haverford College Faculty Research Grant (W.F.S.) and by a grant from the Howard Hughes Medical Institute (L.D.S.).