DISCHARGE PATTERNS OF MOTONEURONS

描述(申请人摘要)：这项研究的长期目标是 一直在描述参与突触前反应的神经元电路 哺乳动物初级传入神经突触效应的调控 并揭示突触前抑制在脊髓损伤中的作用。 感觉-运动整合。在下一次拨款期间所做的大部分努力 期间将寻址到文件，在麻醉或去脑 CAT，节段性和棘上性控制的选择性 介导初级传入去极化(PAD)的通路上的输入 肌肉和皮肤的传入。工作假说是， 传入纤维的脊髓内分支不是强制路径 信息传输，但表示可用于 将信息流引导到不同的神经元集合根据 要执行的功能。为此，感官和 在通向PAD的两条经络的通路上的下行输入 单个Ia、Ib或皮肤纤维，其中一个侧支终止于 L6节段水平的中间核或背角，另一 侧支在L3水平升至Clarke S柱或升至背侧 将分别比较柱状原子核。PAD将从 每个抵押品的椎管内阈值的变化。中美之间的差异 影响的大小将归因于行动的选择性 由刺激的通路施加在两条络脉上。的影响 静息垫和由感官引起的垫上的可逆棘化 节段(L6)和上行(L3)侧支的下行刺激 同样的肌肉或皮肤传入也将被检查，以及 条件反射对Ia纤维静息垫和诱发垫的抑制作用 刺激皮肤和关节神经。 先前的研究表明，刺激网状结构 形成在相当数量的传入纤维中产生PAD 周围神经挤压后1-3个月与肌梭重新连接。 这些效应被归因于脊椎的重组 通路是受损纤维的中介垫。这里提出的实验是 设计用于检查i)生产的衬垫是否在传入端重新连接 肌梭与突触前抑制有关II)GABA能 PAD和突触前抑制的性质 重新连接的传入III)由以下因素产生的垫片的程度 对球网状结构的刺激仅限于受损的 传入和四)其他因素所产生的影响的可能变化 下行输入(大脑皮层、中缝核团和红核)。 第三个项目的目的是检查 背角神经元和中间核中间神经元的种群 介导非交互突触后抑制(I类)或PAD(类 Ii)。计算机技术将被用来揭示a)脊柱 与班级自发活动同步出现的势 I或II类中间神经元，b)脊髓内的位置 相应的脐带电位，c)在以下情况下产生的变化 阿司匹林诱发的胞外场电位和神经元间活动 肌肉和皮肤传入的刺激和下行 (网状脊髓和皮质脊髓)传入之前有脊髓电位 与I类或II类中间神经元的活动有关。这些 问题与功能关系的理解相关 已定义的脊髓中间神经元集合之间的关系及其在 通过传入光纤传输的信息的调制。

DESCRIPTION (Applicant's abstract): The long term goal of this research has been to characterize the neuronal circuitry involved in the presynaptic control of the synaptic effectiveness of primary afferents in the mammalian spinal cord and to disclose the role played by presynaptic inhibition in sensory-motor integration. Most of the effort made during the next grant period will be addressed to document, in the anesthetized or decerebrated cat, the selectivity of the control exerted by segmental and supraspinal inputs on the pathways mediating primary afferent depolarization (PAD) of muscle and cutaneous afferents. The working hypothesis is that the intraspinal branches of afferent fibers are not obliged routes for information transmission but represent potential routes that can be used to direct the information flow to different sets of neurons according to the function to be performed. To this end, the effects of sensory and descending inputs on the pathways leading to PAD of two collaterals of individual Ia, Ib or cutaneous fibers, one collateral ending within the intermediate nucleus or dorsal horn at the L6 segmental level, and the other collateral ascending to Clarke s columns at the L3 level or to the dorsal column nuclei, respectively, will be compared. PAD will be inferred from changes in the intraspinal threshold of each collateral. Differences in the magnitude of the effects will be attributed to selectivity in the action exerted by the stimulated pathways on both collaterals. The effects of reversible spinalization on the resting PAD and on the PAD evoked by sensory and descending stimuli in segmental (L6) and ascending (L3) collaterals of the same muscle or cutaneous afferent will also be examined, as well as the inhibition of the resting and evoked PAD in Ia fibers following conditioning stimulation of cutaneous and joint nerves. Previous investigations have indicated that stimulation of the reticular formation produces PAD in a substantial number of afferent fibers reconnected with muscle spindles 1-3 months after a peripheral nerve crush. These effects have been attributed to a reorganization of the spinal pathways mediating PAD of the damaged fibers. Experiments proposed here are designed to examine i) if the PAD produced in afferents reconnected with muscle spindles is associated with presynaptic inhibition ii) the GABAergic nature of the PAD and of the presynaptic inhibition produced in the reconnected afferents iii) the extent to which the PAD produced by stimulation of the bulbar reticular formation is restricted to the damaged afferents and iv) possible changes in the effects produced by other descending inputs (cerebral cortex, raphe nuclei and red nucleus). A third project aims to examine the functional relationship between populations of dorsal horn neurons and intermediate nucleus interneurons mediating non-reciprocal postsynaptic inhibition (class I) or PAD (class II). Computational techniques will be used to disclose a) the spinal potentials which appear in synchrony with the spontaneous activity of class I or class II interneurons, b) the instraspinal location of the corresponding cord potentials, c) the changes produced when the extracellular field potentials and interneuronal activity evoked by stimulation of muscle and cutaneous afferents and by descending (reticulo-spinal and cortico-spinal) inputs is preceded by cord potentials associated with the activity of class I or class II interneurons. These issues are relevant for the understanding of the functional relationships between defined sets of spinal interneurons and their possible role in the modulation of information conveyed by afferent fibers.