Soma size distinguishes projection neurons from neurokinin 1 receptor-expressing interneurons in lamina I of the rat lumbar spinal dorsal horn.
Soma size distinguishes projection neurons from neurokinin 1 receptor-expressing interneurons in lamina I of the rat lumbar spinal dorsal horn.
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DOI：
10.1016/j.neuroscience.2009.09.071
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发表时间：
2009-12-29
期刊：
影响因子：
3.3
通讯作者：
Todd, A. J.
中科院分区：
文献类型：
--
作者：
Al Ghamdi, K. S.;Polgar, E.;Todd, A. J.
关键词：
脊髓背角的椎板I包含投射到大脑各个区域的神经元，这些投射细胞中约80%表达神经激肽1受体（NK1r），这是p物质的主要受体。在椎板I中发现了两种NK1r免疫反应性神经元：小的弱免疫反应细胞和大的具有强免疫标记的细胞[神经科学97:335-345]。本研究的主要目的是验证大细胞为投射神经元，小细胞为中间神经元的假设。通过向髓质尾侧腹外侧和外侧臂旁区注射示踪剂鉴定投射神经元，并结合NK1r免疫染色。我们发现nk1r免疫反应神经元的大小呈双峰分布。小细胞（体截面积<200 μm2）免疫反应性较弱，大细胞免疫染色强度不同。几乎所有（99%）胞体面积为bbb200 μm2的免疫反应细胞都被逆行标记，而只有10%逆行标记的细胞小于此值。缺乏NK1r的逆行标记神经元的胞体大小与表达NK1r的投射神经元的胞体大小没有差异。有研究表明，缺乏NK1r的小锥体投射神经元群体可能对应于被无害冷却激活的细胞，因此我们评估了非NK1r免疫反应的逆行标记细胞的形态。其中15%是锥体，但它们与锥体nk1r免疫反应性投射神经元的大小没有区别。这些结果证实，大的nk1r免疫反应的I层神经元是投射细胞，小的细胞是中间神经元。由于几乎所有胞体大小为bb0 200 μm2的nk1r免疫反应细胞都被逆行标记，因此在解剖研究中可将此类细胞鉴定为投射细胞。
Lamina I of the spinal dorsal horn contains neurons that project to various brain regions, and ∼80% of these projection cells express the neurokinin 1 receptor (NK1r), the main receptor for substance P. Two populations of NK1r-immunoreactive neurons have been identified in lamina I: small weakly immunoreactive cells and large cells with strong immunolabelling [ Neuroscience 97:335–345]. The main aim of this study was to test the hypothesis that the large cells are projection neurons and that the small cells are interneurons. Projection neurons were identified by injection of tracers into the caudal ventrolateral medulla and lateral parabrachial area, and this was combined with immunostaining for NK1r. We found a bimodal size distribution for NK1r-immunoreactive neurons. The small cells (with somatic cross-sectional areas <200 μm2) showed weak immunoreactivity, while immunostaining intensity was variable among the large cells. Virtually all (99%) of the immunoreactive cells with soma areas >200 μm2 were retrogradely labelled, while only 10% of retrogradely labelled cells were smaller than this. Soma sizes of retrogradely labelled neurons that lacked NK1r did not differ from those of NK1r-expressing projection neurons. It has been suggested that a population of small pyramidal projection neurons that lack NK1r may correspond to cells activated by innocuous cooling, and we therefore assessed the morphology of retrogradely labelled cells that were not NK1r-immunoreactive. Fifteen percent of these were pyramidal, but these did not differ in size from pyramidal NK1r-immunoreactive projection neurons. These results confirm that large NK1r-immunoreactive lamina I neurons are projection cells, and suggest that the small cells are interneurons. Since almost all of the NK1r-immunoreactive cells with soma size >200 μm2 were retrogradely labelled, cells of this type can be identified as projection cells in anatomical studies.
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