Simon E, Schmid H A, Pehl U
Max-Planck-Institute for Physiological and Clinical Research, William G. Kerckhoff-Institute, Bad Nauheim, Germany.
Prog Brain Res. 1998;115:25-47. doi: 10.1016/s0079-6123(08)62028-2.
In the spinal cord, temperature signals are generated which serve as specific inputs in the central nervous control of body temperature. Because of the spatially distinct organization of afferent and efferent neuronal systems at the spinal level, the afferent pathway for temperature signal transmission could be identified in vivo in the ascending, anterior and lateral tracts with a relationship of about 75:25% between warm and cold sensitive neuraxons. Analysis of spinal neuronal thermosensitivity in vitro on spinal cord tissue slices has been concerned, so far, with the superficial laminae of the dorsal horn as the site of origin of ascending nerve fibers conveying mostly temperature and pain signals, and with lamina X as a site of origin of afferent as well as efferent neurons. A relationship of about 95:5% between warm and cold sensitive neurons was found at the segmental level, indicating that warm sensitivity is the prevailing, primary property of spinal neurons, whereas cold sensitivity seems to be mainly generated by synaptic interaction as a secondary modality. Dynamic responses to temperature changes were frequently displayed in vitro at the spinal segmental level in lamina I + II but not in lamina X, even by neurons whose static activity was little influenced by local temperature. Dynamic thermosensitivity was found less frequently in ascending tract neuraxons and was not observed in hypothalamic neurons receiving temperature signal inputs from the spinal cord, and thus, does not seem to be relevant for the thermosensory function of spinal cord neurons, unlike peripheral warm and cold receptors. A majority of spinal warm sensitive neurons displayed both static and dynamic warm sensitivity as an inherent property after synaptic blockade. In the further analysis of spinal cord thermosensitivity, the in vitro approach permits application of the same electrophysiological and neuropharmacological methods as were established for the analysis of hypothalamic thermosensitivity. In addition, the topography of the spinal cord will provide additional structural and possibly histochemical information to characterize the functions of neurons independently of their thermal properties.
在脊髓中会产生温度信号，这些信号在体温的中枢神经控制中作为特定输入。由于脊髓水平上传入和传出神经元系统在空间上的不同组织，温度信号传递的传入途径可以在体内在上升的前束和外侧束中得以识别，其中温敏和冷敏神经轴突的比例约为75:25%。迄今为止，对脊髓组织切片上脊髓神经元热敏感性的体外分析主要关注背角浅层，其为主要传递温度和疼痛信号的上升神经纤维的起源部位，以及X层，其为传入和传出神经元的起源部位。在节段水平发现温敏和冷敏神经元的比例约为95:5%，这表明温敏是脊髓神经元的主要、占主导的特性，而冷敏似乎主要是由突触相互作用作为次要方式产生的。即使是静态活动受局部温度影响很小的神经元，在体外脊髓节段水平的I + II层中也经常表现出对温度变化的动态反应，而在X层中则没有。在上升束神经轴突中较少发现动态热敏感性，并且在接受来自脊髓的温度信号输入的下丘脑神经元中未观察到，因此，与外周温敏和冷敏感受器不同，动态热敏感性似乎与脊髓神经元的热感觉功能无关。大多数脊髓温敏神经元在突触阻断后表现出静态和动态温敏，这是其固有特性。在对脊髓热敏感性的进一步分析中，体外方法允许应用与用于分析下丘脑热敏感性相同的电生理和神经药理学方法。此外，脊髓的拓扑结构将提供额外的结构以及可能的组织化学信息，以独立于神经元的热特性来表征其功能。
