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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: BACKGROUND, METHODS, RESULTS. Meshes: Anesthetics, Local, Animals, Animals, Newborn, Behavior, Animal, Electric Stimulation, Female, Foot, Hyperalgesia, Male, Medulla Oblongata, Nerve Block, Neurons, Afferent, Rats, Rats, Sprague-Dawley, Reflex, Sciatic Nerve, Sensory Thresholds.
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Does surgical injury in the neonatal rat alter the adult pattern of descending modulation from the rostroventral medulla? Context: 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. 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. 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.
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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. Final Decision: yes