Abstract
Pain in infancy influences pain reactivity in later life, but how and why this occurs is poorly understood. Here we review the evidence for developmental plasticity of nociceptive pathways in animal models and discuss the peripheral and central mechanisms that underlie this plasticity. Adults who have experienced neonatal injury display increased pain and injury-induced hyperalgesia in the affected region but mild injury can also induce widespread baseline hyposensitivity across the rest of the body surface, suggesting the involvement of several underlying mechanisms, depending upon the type of early life experience. Peripheral nerve sprouting and dorsal horn central sensitization, disinhibition and neuroimmune priming are discussed in relation to the increased pain and hyperalgesia, while altered descending pain control systems driven, in part, by changes in the stress/HPA axis are discussed in relation to the widespread hypoalgesia. Finally, it is proposed that the endocannabinoid system deserves further attention in the search for mechanisms underlying injury-induced changes in pain processing in infants and children.
Highlights
Pain and injury in early life can cause lasting changes to developing somatosensory and pain systems
By the time preterm infants reach term, they are already displaying enhanced cortical activity to an acute noxious stimulation compared with age-matched term-born controls (Slater et al, 2010a) and later in childhood these children display considerable alterations in somatosensory and pain processing (Hohmeister et al, 2009; Walker et al, 2009b)
Studies show that both preterm and full-term children with neonatal intensive care unit (NICU) experience display greater perceptual sensitization to tonic heat (Hohmeister et al, 2009) accompanied by a generalized decreased sensitivity to cutaneous thermal (Walker et al, 2009b) and mechanical (Schmelzle-Lubiecki et al, 2007) stimulation
Summary
European Journal of Neuroscience, Vol 39, pp. 344–352, 2014 doi:10.1111/ejn.12414. The consequences of pain in early life: injury-induced plasticity in developing pain pathways. European Journal of Neuroscience, Vol 39, pp. The consequences of pain in early life: injury-induced plasticity in developing pain pathways. Fred Schwaller and Maria Fitzgerald Department of Neuroscience, Physiology & Pharmacology, University College London, London, UK
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