Light A R, Trevino D L, Perl E R
J Comp Neurol. 1979 Jul 15;186(2):151-71. doi: 10.1002/cne.901860204.
Functional characteristics of spinal neurons located in the marginal zone (lamina I) and substantia gelatinosa (lamina II) were compared to their structural features by intrcellularly staining the source of unitary potentials with horseradish peroxidase (HRP) in unanesthetized, spinal cats. The responses of postsynaptic units to graded electrical volleys in intact dorsal roots and to physiological stimulation revealed that the peripheral excitatory input to neurons of the region is dominated by slowly conducting afferent fibers; often, the input to a given element is largely from a particular class of receptors. One type commonly seen received its principal peripheral excitation from low threshold mechanoreceptors with A delta or C afferent fibers. Mechanoreceptive elements often exhibited a marked, prolonged habituation and many were not excited by afferent volleys. Other units were predominantly excited by nociceptors with myelinated or unmyelinated fibers, or by thermoreceptors with unmyelinated fibers. A few units (principally the thermoreceptive) showed substantial ongoing activity which was modulated by sensory stimulation, but most had little or none. The HRP staining revealed neuronal morphology in fine detail. No relationship between neuronal configuration and physiological response was discerned. Soma location was not always linked to afferent input, although the cell bodies of nociceptive and thermoreceptive neurons tended to be in lamina I or outer lamina II (SGo) while those of the innocuous mechanoreceptive meurons tended to be in inner lamina II (SGi). The locus of a neuron's major dendritic arborization was more closely related to the source(s) of peripheral excitation. Cells excited by nociceptors with myelinated fibers had major dendritic projections in the marginal zone. Cells excited by nociceptors or thermoreceptors with unmyelinated fibers had important dendritic branching in the SGo. Innocuous mechanoreceptive neurons had primary dendritic arborization in the SGi when the input derived from unmyelinated fibers, or in the SGi and extending into the outer nucleus proprius (lamina III) when the afferent drive came from A delta fibers. These findings support the concept that laminae I and II constitute a major termination region for thin primary afferent fibers, myelinated fibers from nociceptors ending principally in lamina I and unmyelinated fibers from nociceptors, thermoreceptors, and mechanoreceptros terminating predominantly in lamina II. Substantial integrative and distributive functions can be expected of such an afferent termination zone.
在未麻醉的脊髓猫中，通过用辣根过氧化物酶（HRP）对单电位源进行细胞内染色，将位于边缘区（I层）和胶状质（II层）的脊髓神经元的功能特性与其结构特征进行了比较。突触后单位对完整背根中的分级电脉冲以及对生理刺激的反应表明，该区域神经元的外周兴奋性输入主要由传导缓慢的传入纤维主导；通常，给定神经元的输入很大程度上来自特定类别的感受器。一种常见类型主要从具有Aδ或C传入纤维的低阈值机械感受器接受主要的外周兴奋。机械感受性神经元常常表现出明显的、持续时间长的习惯化，并且许多神经元不会被传入脉冲所兴奋。其他单位主要由具有有髓或无髓纤维的伤害感受器或具有无髓纤维的温度感受器兴奋。少数单位（主要是温度感受性单位）表现出大量的持续活动，这种活动受到感觉刺激的调节，但大多数单位几乎没有或没有持续活动。HRP染色详细显示了神经元形态。未发现神经元形态与生理反应之间的关系。胞体位置并不总是与传入输入相关联，尽管伤害性和温度感受性神经元的胞体倾向于位于I层或II层外层（SGo），而无害机械感受性神经元的胞体倾向于位于II层内层（SGi）。神经元主要树突分支的位置与外周兴奋的来源更密切相关。由具有有髓纤维的伤害感受器兴奋的细胞在边缘区有主要的树突投射。由具有无髓纤维的伤害感受器或温度感受器兴奋的细胞在SGo有重要的树突分支。当输入来自无髓纤维时，无害机械感受性神经元在SGi有初级树突分支，当传入驱动来自Aδ纤维时，其初级树突分支在SGi并延伸到外固有核（III层）。这些发现支持了这样一种概念，即I层和II层构成了细的初级传入纤维的主要终止区域，来自伤害感受器的有髓纤维主要终止于I层，来自伤害感受器、温度感受器和机械感受器的无髓纤维主要终止于II层。可以预期这样一个传入终止区具有大量的整合和分布功能。
