Departments of Neurology and Physiology, Emory University School of Medicine, Atlanta GA 30322, USA.
Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, GA 30322, USA.
Neural Plast. 2019 Nov 19;2019:6147878. doi: 10.1155/2019/6147878. eCollection 2019.
Electrical stimulations of dorsal cutaneous nerves (DCNs) at each lumbothoracic spinal level produce the bilateral cutaneus trunci muscle (CTM) reflex responses which consist of two temporal components: an early and late responses purportedly mediated by A and C fibers, respectively. We have previously reported central projections of DCN A and C fibers and demonstrated that different projection patterns of those afferent types contributed to the somatotopic organization of CTM reflex responses. Unilateral hemisection spinal cord injury (SCI) was made at T10 spinal segments to investigate the plasticity of early and late CTM responses 6 weeks after injury. Both early and late responses were drastically increased in response to both ipsi- and contralateral DCN stimulations both above (T6 and T8) and below (T12 and L1) the levels of injury demonstrating that nociceptive hyperreflexia developed at 6 weeks following hemisection SCI. We also found that DCN A and C fibers centrally sprouted, expanded their projection areas, and increased synaptic terminations in both T7 and T13, which correlated with the size of hemisection injury. These data demonstrate that central sprouting of cutaneous afferents away from the site of injury is closely associated with enhanced responses of intraspinal signal processing potentially contributing to nociceptive hyperreflexia following SCI.
电刺激每个胸腰脊神经的背皮神经（DCN）会产生双侧的腹肌反射（CTM）反应，其由两个时相组成：早期和晚期反应，分别由 A 和 C 纤维介导。我们之前已经报告了 DCN A 和 C 纤维的中枢投射，并证明了这些传入类型的不同投射模式有助于 CTM 反射反应的躯体定位组织。在 T10 脊髓节段进行单侧半切脊髓损伤（SCI），以研究损伤后 6 周时早期和晚期 CTM 反应的可塑性。在损伤水平以上（T6 和 T8）和以下（T12 和 L1）的同侧和对侧 DCN 刺激下，早期和晚期反应都明显增加，表明半切 SCI 后 6 周出现了伤害性反射亢进。我们还发现，DCN A 和 C 纤维在中枢发芽，扩大了它们的投射区域，并在 T7 和 T13 增加了突触末端，这与半切损伤的大小有关。这些数据表明，远离损伤部位的皮肤传入纤维的中枢发芽与脊髓内信号处理增强反应密切相关，这可能有助于 SCI 后的伤害性反射亢进。
