Antal Zs, Luz L L, Safronov B V, Antal M, Szücs Peter
Department of Anatomy, Histology and Embryology, Univerity of Debrecen, Nagyerdei krt. 98, Debrecen, 4032, Hungary.
Neuronal Networks Group, Instituto de Biologia Molecular e Celular-IBMC, Universidade do Porto, Rua do Campo Alegre 823, 4150-180, Porto, Portugal.
Brain Struct Funct. 2016 May;221(4):2343-60. doi: 10.1007/s00429-015-1046-3. Epub 2015 Apr 26.
The role of spinal dorsal horn propriospinal connections in nociceptive processing is not yet established. Recently described, rostrocaudally oriented axon collaterals of lamina I projection and local-circuit neurons (PNs and LCNs) running in the dorsolateral funiculus (DLF) may serve as the anatomical substrate for intersegmental processing. Putative targets of these axons include lateral dendrites of superficial dorsal horn neurons, including PNs, and also neurons in the lateral spinal nucleus (LSN) that are thought to be important integrator units receiving, among others, visceral sensory information. Here we used an intact spinal cord preparation to study intersegmental connections within the lateral part of the superficial dorsal horn. We detected brief monosynaptic and prolonged polysynaptic excitation of lamina I and LSN neurons when stimulating individual dorsal horn neurons located caudally, even in neighboring spinal cord segments. These connections, however, were infrequent. We also revealed that some projection neurons outside the dorsal grey matter and in the LSN have distinct, previously undescribed course of their projection axon. Our findings indicate that axon collaterals of lamina I PNs and LCNs in the DLF rarely form functional connections with other lamina I and LSN neurons and that the majority of their targets are on other elements of the dorsal horn. The unique axon trajectories of neurons in the dorsolateral aspect of the spinal cord, including the LSN do not fit our present understanding of midline axon guidance and suggest that their function and development differ from the neurons inside lamina I. These findings emphasize the importance of understanding the connectivity matrix of the superficial dorsal horn in order to decipher spinal sensory information processing.
脊髓背角固有脊髓连接在伤害性信息处理中的作用尚未明确。最近有描述称，在背外侧索（DLF）中走行的I层投射神经元和局部回路神经元（PNs和LCNs）的 rostrocaudally 定向轴突侧支可能是节段间处理的解剖学基础。这些轴突的假定靶点包括浅表背角神经元的外侧树突，包括PNs，以及脊髓外侧核（LSN）中的神经元，这些神经元被认为是重要的整合单元，接收包括内脏感觉信息在内的多种信息。在这里，我们使用完整的脊髓标本研究浅表背角外侧部分内的节段间连接。当刺激位于尾侧的单个背角神经元时，即使在相邻脊髓节段，我们也检测到I层和LSN神经元的短暂单突触和延长的多突触兴奋。然而，这些连接并不常见。我们还发现，背侧灰质外和LSN中的一些投射神经元有独特的、以前未描述过的投射轴突走行。我们的研究结果表明，DLF中I层PNs和LCNs的轴突侧支很少与其他I层和LSN神经元形成功能连接，并且它们的大多数靶点位于背角的其他成分上。脊髓背外侧方面包括LSN的神经元的独特轴突轨迹不符合我们目前对中线轴突导向的理解，表明它们的功能和发育与I层内的神经元不同。这些发现强调了理解浅表背角连接矩阵以破译脊髓感觉信息处理的重要性。
