THE SPINOMESENCEPHALIC TRACT: ANATOMY AND PHYSIOLOGY

本研究计划的两个主要目标是研究：(A) 神经回路和(B)突触机制。 猫脊髓大脑区的反应和感受野特征 束(SMT)细胞。这些目标将通过三种类型的 实验。(1)细胞内注射辣根过氧化物酶 将被用来研究细胞形态和树突分枝 具有功能特征的SMT细胞。(2)电刺激 位于不同脑干水平的电极将用于标测 产生兴奋和/或抑制作用的部位的分布 不同类别的SMT细胞。脊柱损伤也将被用来 定位引起这些的下行路径的脊椎轨迹 影响并确定复杂感受野的程度 SMT细胞的减少是由于脊柱上结构的下行影响 和/或脊髓内的局部回路。(3)使用细胞内 外周刺激对脑电活动的抑制作用 将对SMT细胞进行研究，以确定这些影响是否是由于前 和/或突触后机制。研究计划的第三个目标 是进一步评估SMT对不同中脑区域的投影。 这将通过系统地绘制终止地点(S)来进行研究 采用逆行激活技术的SMT轴突移植。逆行 阈值图将延伸到内侧和外侧丘脑 努力研究CAT SMT轴突的侧支作用。以前的研究 与CAT 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神经元的异质性群体 性质，脊椎起源，轴突轨迹和终止位置。 这一通路在伤害性感受中的潜在参与是由 大多数SMT细胞对有害物质有反应的证据 机械和热刺激。与解剖学相关的其他研究 而这一途径的生理学将有助于我们理解 潜在地负责多维方面的底物 疼痛。除了提供更好的了解解剖学和 SMT细胞的生理学，上述研究的具体目的 意在扩展我们对感官机制的基本知识 脊髓，尤其是与伤害性感觉有关的脊髓。

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.