Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom.
Ann N Y Acad Sci. 2013 Mar;1279:97-102. doi: 10.1111/nyas.12033.
Developing brain circuits are shaped by postnatal sensory experience, but little is known about this process at the level of the spinal cord. Here we review the mechanisms by which cutaneous sensory input drives the maturation of spinal sensory circuits. Newborn animals are highly sensitive to tactile input and dorsal horn circuits are dominated by low threshold A fiber inputs. We show that this arises from the absence of the functional, targeted glycinergic inhibition of tactile activity that emerges only in the second week of life. Selective block of afferent C fibers in postnatal week 2 delays the maturation of glycinergic inhibition and maintains dorsal horn circuits in a neonatal state. We propose that in the newborn strong tactile A fiber input facilitates activity-dependent synaptic strengthening in the dorsal horn, but that this ends with the arrival of nociceptive C fiber spinal input that drives the maturation of targeted glycinergic inhibition.
发育中的大脑回路受到出生后感觉体验的影响，但脊髓水平的这一过程知之甚少。本文综述了皮肤感觉输入驱动脊髓感觉回路成熟的机制。新生动物对触觉输入高度敏感，背角回路主要由低阈值 A 纤维输入支配。我们发现，这是由于缺乏功能性的、靶向的甘氨酸能抑制触觉活动，而这种抑制仅在生命的第二周才出现。在出生后第 2 周选择性阻断传入 C 纤维可延迟甘氨酸能抑制的成熟，并使背角回路保持在新生儿状态。我们提出，在新生儿中，强烈的触觉 A 纤维输入促进了背角中活动依赖性突触强化，但随着伤害性 C 纤维传入脊髓输入的出现，这种强化会结束，从而驱动靶向甘氨酸能抑制的成熟。
