Long-Term Consequences of Neonatal Injury

Abstract

The maturation of the central nervous system's (CNS's) sensory connectivity is driven by modality-specific sensory input in early life. For the somatosensory system, this input is the physical, tactile interaction with the environment. Nociceptive circuitry is functioning at the time of birth; however, there is still considerable organization and refinement of this circuitry that occurs postnatally, before full discrimination of tactile and noxious input is possible. This fine-tuning involves separation of tactile and nociceptive afferent input to the spinal cord's dorsal horn and the maturation of local and descending inhibitory circuitry. Disruption of that input in early postnatal life (for example, by tissue injury or other noxious stimulus), can have a profound influence on subsequent development, and consequently the mature functioning of pain systems. In this review, the impact of neonatal surgical incision on nociceptive circuitry is discussed in terms of the underlying developmental neurobiology. The changes are complex, occurring at multiple anatomical sites within the CNS, and including both neuronal and glial cell populations. The altered sensory input from neonatal injury selectively modulates neuronal excitability within the spinal cord, disrupts inhibitory control, and primes the immune system, all of which contribute to the adverse long-term consequences of early pain exposure. W W W Conséquences à long terme d'une blessure néonataleLa maturation de la connectivité sensorielle du système nerveux central (SNC) est dictée par les intrants sensoriels propres aux modalités, en début de vie. Pour le système somatosensoriel, ces intrants sont l'interaction physique, tactile avec l'environnement. La circuiterie nociceptive fonctionne au moment de la naissance; cependant, une part considérable de l'organisation et du raffinement de cette circuiterie se produit en période postnatale, avant que la pleine discrimination entre intrants tactiles et nuisibles ne soit possible. Ce raffinement implique la séparation des intrants afférents tactiles et nociceptifs à la corne dorsale de la moelle épinière, et la maturation de la circuiterie inhibitoire locale et descendante. La perturbation de ces intrants en début de vie postnatale (par exemple, par une lésion des tissus ou un autre stimulus nuisible) peut avoir une influence profonde sur le développement subséquent et par conséquent, sur le fonctionnement mature des systèmes de la douleur. Dans cette revue, nous présentons l'impact d'une incision chirurgicale néonatale sur la circuiterie nociceptive, en ce qui concerne la neurobiologie développementale sous-jacente. Les changements sont complexes et se produisent à de multipes sites anatomiques du SNC, incluant des populations cellulaires à la fois neuronales et gliales. Les intrants sensoriels altérés par une blessure néonatale modulent sélectivement l'excitabilité neuronale de la moelle épinière, perturbent le contrôle inhibitoire, et préparent le système immunitaire, et tout cela contribue à des conséquences i...

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