Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.
Neuronal Networks Group, Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal.
Pain. 2018 Nov;159(11):2214-2222. doi: 10.1097/j.pain.0000000000001320.
The dorsal horn of the spinal cord (laminae I-VI) processes diverse modalities of nociceptive and nonnociceptive sensory information. Antenna-type neurons with cell bodies located in lamina III and large dendritic trees extending from the superficial lamina I to deep lamina IV are best shaped for the integration of a wide variety of inputs arising from primary afferent fibers and intrinsic spinal circuitries. Although the somatodendritic morphology, the hallmark of antenna neurons, has been well studied, little is still known about the axon structure and basic physiological properties of these cells. Here, we did whole-cell recordings in a rat (P9-P12) spinal cord preparation with attached dorsal roots to examine the axon course, intrinsic firing properties, and primary afferent inputs of antenna cells. Nine antenna cells were identified from a large sample of biocytin-filled lamina III neurons (n = 46). Axon of antenna cells showed intensive branching in laminae III-IV and, in half of the cases, issued dorsally directed collaterals reaching lamina I. Antenna cells exhibited tonic and rhythmic firing patterns; single spikes were followed by hyperpolarization or depolarization. The neurons received monosynaptic inputs from the low-threshold Aβ afferents, Aδ afferents, as well as from the high-threshold Aδ, and C afferents. When selectively activated, C-fiber-driven monosynaptic and polysynaptic excitatory postsynaptic potentials were sufficiently strong to evoke firing in the neurons. Thus, lamina III antenna neurons integrate low-threshold and nociceptive high-threshold primary afferent inputs and can function as wide dynamic range neurons able to directly connect deep dorsal horn with the major nociceptive projection area lamina I.
脊髓背角（I-VI 层）处理各种形式的伤害性和非伤害性感觉信息。位于 III 层的细胞体和从浅层 I 层延伸到深层 IV 层的大型树突的天线型神经元最适合整合来自初级传入纤维和固有脊髓回路的各种输入。尽管天线神经元的体细胞形态学已经得到了很好的研究，但对于这些细胞的轴突结构和基本生理特性仍知之甚少。在这里，我们在一个带有附着的背根的大鼠（P9-P12）脊髓制备物中进行全细胞记录，以检查天线细胞的轴突过程、内在放电特性和初级传入输入。从大量填充有生物胞素的 III 层神经元（n = 46）中鉴定出 9 个天线细胞。天线细胞的轴突在 III-IV 层中表现出密集的分支，在一半的情况下，发出背向的侧支到达 I 层。天线细胞表现出紧张和节律性的放电模式；单个尖峰后紧接着是超极化或去极化。神经元接受来自低阈值 Aβ传入、Aδ传入以及来自高阈值 Aδ和 C 传入的单突触输入。当选择性激活时，C 纤维驱动的单突触和多突触兴奋性突触后电位足够强，可以在神经元中引发放电。因此，III 层天线神经元整合低阈值和伤害性高阈值初级传入输入，并可以作为宽动态范围神经元，能够直接将深部背角与主要伤害性投射区 I 层连接。
