DISCHARGE PATTERNS OF MOTONEURONS

这项研究的长期目标是识别出 介导初级传入去极化（PAD）的gr. I肌肉和 猫脊髓中的皮肤纤维，并更精确地定义 它们所属的反射途径，以及脊髓上的影响， 调节它们的活动。 将特别注意 确定介导I类纤维PAD的中间神经元是否属于 仅执行突触前动作的私人通路，或者它们是否是共享的 也通过在运动神经元中产生突触后抑制的途径。 我--在麻醉的猫中，将同时进行细胞外记录 由中间核的中间神经元和背根组成， 腹根花丝，在后者的情况下使用蔗糖间隙 法 尖峰触发平均将用于增强任何背 根电位和/或腹根电位，其时间锁定到 神经元间活动 这将允许揭示突触 中间神经元与传入纤维和/或运动神经元的连接。 详细研究这些中间神经元对 还将进行节段和棘上输入，以确定 它们所属的反射路径。 将尝试记录 细胞内从PAD介导的中间神经元，并将它们注射 辣根过氧化物酶用于其形态学表征。 二、我们之前的调查表明，有两个独立的 介导Ia的PAD的中间核中间神经元组 这些纤维受到来自脑干的相反作用。 以来 伸肌Ⅰ类纤维的分类标准 肌肉是基于由刺激产生的PAD的模式 这些研究现在将扩展到gr. I纤维， 后二头肌-半腱肌，其中分类组Ia和Ib 纤维就不那么模棱两可了。 预计这些调查将提供 关于中间神经元的功能组织的信息 其介导屈肌和伸肌的Ia组纤维的PAD。 III.我们将研究平均值、方差和相关性的变化， 单纤维Ia单突触EPSP同时记录， 运动神经元对在不同量的激动剂拉伸和 拮抗肌 将特别注意可能出现的 存在两个EPSP中产生的相关故障 运动神经元作为突触前末梢传导阻滞的证据。

The long term goals of this research are to identify the interneurons which mediate the primary afferent depolarization (PAD) of gr. I muscle and of cutaneous fibers in the cat spinal cord, and to define more precisely the reflex pathways to which they belong, as well as the supraspinal influences which modulate their activity. Particular attention will be given to determine if the interneurons mediating the PAD of gr. I fibers belong to private pathways exerting presynaptic actions only, or if they are shared also by pathways producing post-synaptic inhibition in motoneurons. I.- In the anesthetized cat, simultaneous extracellular recordings will be made from interneurons in the intermediate nucleus and from dorsal root and ventral root filaments, using in the latter case the sucrose gap technique. Spike triggered averages will be used to enhance any dorsal root and/or ventral root potentials which are time locked to the interneuronal activity. This will allow disclosure of the synaptic connections of the interneurons with afferent fibers and/or motoneurons. Detailed investigation of the responsee patterns of these interneurons to segmental and supraspinal inputs will be also made in order to define the reflex pathways to which they belong. Attempts will be made to record intracellularly from the PAD mediating interneurons and to inject them with horse-radish peroxidase for their morphological characterization. II.- Our previous investigations suggest that there are two independent sets of intermediate nucleus interneurons mediating the PAD of the Ia fibers which are subjected to opposite actions from the brain-stem. since the criteria which we have used to classify gr. I fibers of extensor muscles have been based on the patterns of the PAD produced by stimulation of afferent nerves, these studies will now be extended to gr. I fibers from the posterior biceps-semitendinosus where classification of gr. Ia and Ib fibers is less equivocal. These investigations are expected to provide information pertaining the functional organization of the interneurons which mediate the PAD of the gr. Ia fibers of flexors and extensors. III.- We will study the changes in the mean, variance and correlation of the single fiber Ia monosynaptic EPSPs recorded simultaneously from motoneuron pairs during varying amounts of stretch of agonist and antagonist muscles. Particular attention will be given to the possible existence of correlated failures of the EPSPs generated in the two motoneurons as evidence for conduction blockade in presynaptic terminals.