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Surgical injury in the neonatal rat alters the adult pattern of descending modulation from the rostroventral medulla

Walker, Suellen M.; Fitzgerald, Maria; Hathway, Gareth J.

Authors

Suellen M. Walker s.wallker@ucl.ac.uk

Maria Fitzgerald m.fitzgerald@ucl.ac.uk



Abstract

Background: Neonatal pain and injury can alter long-term sensory thresholds. Descending rostroventral medulla (RVM) pathways can inhibit or facilitate spinal nociceptive processing in adulthood. As these pathways undergo significant postnatal maturation, the authors evaluated long-term effects of neonatal surgical injury on RVM descending modulation.
Methods: Plantar hind paw or forepaw incisions were performed in anesthetized postnatal day (P)3 Sprague-Dawley rats. Controls received anesthesia only. Hind limb mechanical and thermal withdrawal thresholds were measured to 6 weeks of age (adult). Additional groups received pre- and post-incision sciatic nerve levobupivacaine or saline. Hind paw nociceptive reflex sensitivity was quantified in anesthetized adult rats using biceps femoris electromyography, and the effect of RVM electrical stimulation (5–200 μA) measured as percentage change from baseline.
Results: In adult rats with previous neonatal incision (n = 9), all intensities of RVM stimulation decreased hind limb reflex sensitivity, in contrast to the typical bimodal pattern of facilitation and inhibition with increasing RVM stimulus intensity in controls (n = 5) (uninjured vs. neonatally incised, P < 0.001). Neonatal incision of the contralateral hind paw or forepaw also resulted in RVM inhibition of hind paw nociceptive reflexes at all stimulation intensities. Behavioral mechanical threshold (mean ± SEM, 28.1 ± 8 vs. 21.3 ± 1.2 g, P < 0.001) and thermal latency (7.1 ± 0.4 vs. 5.3 ± 0.3 s, P < 0.05) were increased in both hind paws after unilateral neonatal incision. Neonatal perioperative sciatic nerve blockade prevented injury-induced alterations in RVM descending control.
Conclusions: Neonatal surgical injury alters the postnatal development of RVM descending control, resulting in a predominance of descending inhibition and generalized reduction in baseline reflex sensitivity. Prevention by local anesthetic blockade highlights the importance of neonatal perioperative analgesia.

Journal Article Type Article
Publication Date Jun 1, 2015
Journal Anesthesiology
Print ISSN 0003-3022
Electronic ISSN 1528-1175
Publisher Lippincott, Williams & Wilkins
Peer Reviewed Peer Reviewed
Volume 122
Issue 6
APA6 Citation Walker, S. M., Fitzgerald, M., & Hathway, G. J. (2015). Surgical injury in the neonatal rat alters the adult pattern of descending modulation from the rostroventral medulla. Anesthesiology, 122(6), https://doi.org/10.1097/ALN.0000000000000658
DOI https://doi.org/10.1097/ALN.0000000000000658
Publisher URL http://anesthesiology.pubs.asahq.org/article.aspx?articleid=2276861
Copyright Statement Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by-nc-nd/4.0

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Copyright Statement
Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by-nc-nd/4.0





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