THE SPINOMESENCEPHALIC TRACT: ANATOMY AND PHYSIOLOGY

本研究计划的两个主要目标是研究： 神经元回路和（B）突触机制，有助于 猫脊髓中脑的反应和感受野特性 束（SMT）细胞。 这些目标将通过三种类型的 实验 (1)辣根过氧化物酶的细胞内注射 将用于研究细胞形态和树突状分支， 功能特性的SMT细胞。 (2)电刺激 定位在不同脑干水平的电极将被用于绘制 产生兴奋和/或抑制作用的部位的分布 不同种类的SMT单元。 脊柱病变也将用于 定位负责这些的下行通路的脊柱轨迹 影响，并确定在何种程度上，复杂的感受野 的SMT细胞是由于脊髓上结构的下行影响 和/或脊髓内的局部电路。 (3)使用细胞内 记录技术外周刺激的抑制作用 SMT细胞将进行研究，以确定这些影响是否是由于预- 和/或突触后机制。 研究计划的第三个目标 是进一步评估SMT向不同中脑区域的投射。 这将通过系统地绘制以下终止位点来研究： 使用逆向激活技术的SMT轴突。 逆行 阈值地图将延伸到内侧和外侧丘脑， 努力研究猫SMT轴突的抵押。 以前的研究 与猫SMT相关的研究表明，这条途径由一个 具有不同感受野和反应的异质神经元群体 特性、脊髓起源、轴突轨迹和终止部位。 这一通路在伤害感受中的潜在参与得到以下证据的支持： 证明大多数SMT细胞对有害的 机械和热刺激。 与解剖结构相关的其他研究 这条通路的生理学将有助于我们理解 潜在地负责的多方面的基板 痛苦 除了提供对解剖结构的更好理解， SMT细胞的生理学，上述研究的具体目标 旨在扩展我们对感觉机制的基本知识， 脊髓，特别是与伤害感受有关的脊髓。

Two major objectives of the present research plan are to study the: (a) neuronal circuitry and (b) synaptic mechanisms that contribute to the response and receptive field characteristics of cat spinomesencephalic tract (SMT) cells. These objectives will be addressed by three types of experiments. (1) The intracellular injection of horseradish peroxidase will be used to study the cell morphologies and dendritic arborizations of functionally characterized SMT cells. (2) Electrical stimulation with electrodes positioned at different brainstem levels will be used to map the distribution of sites producing excitatory and/or inhibitory effects on different classes of SMT cells. Spinal lesions will also be used to localize the spinal trajectory of descending pathways responsible for these effects and to determine the extent to which the complex receptive fields of SMT cells are due to the descending influence of supraspinal structures and/or local circuitry within the spinal cord. (3) Using intracellular recording techniques the inhibitory effects of peripheral stimulation on SMT cells will be studied to determine if these effects are due to pre- and/or postsynaptic mechanisms. The third objective of the research plan is to further evaluate the SMT projection to different midbrain regions. This will be studied by systematically mapping the termination site(s) of SMT axons using the technique of antidromic activation. Antidromic threshold maps will extend into the medial and lateral thalamus in an effort to study the collateralization of cat SMT axons. Previous studies related to the cat SMT have shown this pathway to be made up of a heterogenous population of neurons with varied receptive field and response properties, spinal origins, axonal trajectories and sites of termination. The potential involvement of this pathway in nociception is supported by the demonstration that the majority of SMT cells respond to noxious mechanical and thermal stimuli. Additional studies related to the anatomy and physiology of this pathway will contribute to our understanding of substrates potentially responsible for the multidimensional aspects of pain. In addition to providing a better understanding of the anatomy and physiology of SMT cells, the specific aims of the research outlined above are intended to extend our basic knowledge of sensory mechanisms in the spinal cord and particularly that related to nociception.