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The Journal of Neuroscience, August 20, 2003, 23(20):7719-7725

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 Previous Article

Developmental Learning in a Pain-Related System: Evidence for a Cross-Modality Mechanism

Alexandra Waldenström, Jonas Thelin, Erik Thimansson, Anders Levinsson, and Jens Schouenborg

Section of Neurophysiology, Department for Physiological Sciences, Lund University, S-221 84 Lund, Sweden

The nociceptive spinal reflex system performs highly precise sensorimotor transformations that require functionally specified synaptic strengths. The specification is gradually attained during early development and appears to be learning dependent. Here we determine the time course of this specification for heat-nociceptive tail withdrawal reflexes and analyze which types of primary afferents are important for the learning by applying various forms of noninvasive sensory deprivations. The percentage of erroneous heat-nociceptive tail withdrawal reflexes (i.e., movements directed toward the stimulation) decreased gradually from 64.1 ± 2.5% (mean ± SEM) to <10% during postnatal days 10-21. This improvement was completely blocked by anesthetizing the tail during the adaptation period, confirming that an experience-dependent mechanism is involved in the specification of synaptic strengths. However, the results show that the adaptation occurs to a significant extent despite local analgesia and protection of the tail from noxious input, provided that tactile sensitivity is preserved. Therefore, it appears that a nociceptive input is not necessary for the adaptation, and that input from tactile receptors can be used to guide the nociceptive synaptic organization during development. Sensory deprivation in the adult rat failed to affect the heat-nociceptive withdrawal reflex system, indicating that the adaptation has a "critical period" during early development. These findings provide a key to the puzzle of how pain-related systems can be functionally adapted through experience despite the rare occurrence of noxious input during early life.

Key words: pain; somatosensory; activity-dependent learning and memory; spinal cord; sensorimotor transformation; development

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Received Mar. 25, 2003; revised Jun. 27, 2003; accepted Jun. 30, 2003.

This article has been cited by other articles:

				M. Granmo, P. Petersson, and J. Schouenborg Action-Based Body Maps in the Spinal Cord Emerge from a Transitory Floating Organization J. Neurosci., May 21, 2008; 28(21): 5494 - 5503. [Abstract] [Full Text] [PDF]

				L. R. Bremner and M. Fitzgerald Postnatal tuning of cutaneous inhibitory receptive fields in the rat J. Physiol., March 15, 2008; 586(6): 1529 - 1537. [Abstract] [Full Text] [PDF]

				P. Petersson, M. Granmo, and J. Schouenborg Properties of an Adult Spinal Sensorimotor Circuit Shaped Through Early Postnatal Experience J Neurophysiol, July 1, 2004; 92(1): 280 - 288. [Abstract] [Full Text] [PDF]

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