Morphological, biophysical and synaptic properties of glutamatergic neurons of the mouse spinal dorsal horn.
Morphological, biophysical and synaptic properties of glutamatergic neurons of the mouse spinal dorsal horn.
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DOI：
10.1113/jphysiol.2013.264937
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发表时间：
2014-02-15
期刊：
影响因子：
--
通讯作者：
Zeilhofer HU
中科院分区：
文献类型：
--
作者：
Punnakkal P;von Schoultz C;Haenraets K;Wildner H;Zeilhofer HU
脊髓背角的中间神经元是躯体感觉和伤害性加工的中心。对其功能的机械理解取决于对其内在特性的深刻了解以及它们与背角电路的集成。在此，我们使用在泡状谷氨酸转运蛋白（vGluT2）基因控制下表达增强绿色荧光蛋白（eGFP）的BAC转基因小鼠（vGluT2::eGFP小鼠）对兴奋性背角神经元进行了详细的电生理和形态学表征，并将其与GABAergic （Gad67::eGFP标记）和甘氨酸ergic （GlyT2::eGFP标记）神经元的特性进行了比较。在大约三分之一的兴奋性背角神经元中检测到vGluT2::eGFP，正如vGluT2::eGFP与谷氨酸能神经元亚型的不同标记物共同表达所证明的那样，可能标记了这些神经元的代表性部分。在vGluT2::eGFP神经元中发现了三种树突状树形态（垂直、中央和径向），但未发现胰岛细胞型形态。与抑制神经元相比，vGluT2::eGFP神经元具有更多的去极化动作电位阈值和更长的动作电位持续时间，而在静息膜电位、输入电阻、细胞电容和超极化后无显著差异。延迟放电和单动作电位放电分别是背浅角和背深角vGluT2::eGFP神经元中最常见的单一放电模式。相反，在背角的抑制性中间神经元中，强直性放电占优势。辣椒素诱导的突触输入在大约一半的兴奋性和抑制性神经元中被检测到，并且在背角表面神经元中比在背角深部神经元中更频繁地发生。在大多数谷氨酸能和甘氨酸能神经元中发现了原发性传入诱发（多突触）抑制输入，但仅在不到一半的gaba能神经元中发现。因此，兴奋性背角神经元与抑制性背角神经元在一些生物物理特性上不同，也可能在它们与局部神经元回路的整合上不同。
Interneurons of the spinal dorsal horn are central to somatosensory and nociceptive processing. A mechanistic understanding of their function depends on profound knowledge of their intrinsic properties and their integration into dorsal horn circuits. Here, we have used BAC transgenic mice expressing enhanced green fluorescent protein (eGFP) under the control of the vesicular glutamate transporter (vGluT2) gene (vGluT2::eGFP mice) to perform a detailed electrophysiological and morphological characterisation of excitatory dorsal horn neurons, and to compare their properties to those of GABAergic (Gad67::eGFP tagged) and glycinergic (GlyT2::eGFP tagged) neurons. vGluT2::eGFP was detected in about one-third of all excitatory dorsal horn neurons and, as demonstrated by the co-expression of vGluT2::eGFP with different markers of subtypes of glutamatergic neurons, probably labelled a representative fraction of these neurons. Three types of dendritic tree morphologies (vertical, central, and radial), but no islet cell-type morphology, were identified in vGluT2::eGFP neurons. vGluT2::eGFP neurons had more depolarised action potential thresholds and longer action potential durations than inhibitory neurons, while no significant differences were found for the resting membrane potential, input resistance, cell capacitance and after-hyperpolarisation. Delayed firing and single action potential firing were the single most prevalent firing patterns in vGluT2::eGFP neurons of the superficial and deep dorsal horn, respectively. By contrast, tonic firing prevailed in inhibitory interneurons of the dorsal horn. Capsaicin-induced synaptic inputs were detected in about half of the excitatory and inhibitory neurons, and occurred more frequently in superficial than in deep dorsal horn neurons. Primary afferent-evoked (polysynaptic) inhibitory inputs were found in the majority of glutamatergic and glycinergic neurons, but only in less than half of the GABAergic population. Excitatory dorsal horn neurons thus differ from their inhibitory counterparts in several biophysical properties and possibly also in their integration into the local neuronal circuitry.
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