DISCHARGE PATTERNS OF MOTONEURONS

这项研究的长期目标是确定神经元的特征。 参与突触前控制突触有效性的回路 脊椎动物脊髓的初级传入及其在脑内的作用 感觉-运动整合中的突触前抑制。建议数 实验的目的是揭示脊髓上的选择性 对调节初级传入的脊髓通路施加的控制 单个肌梭和肌腱器官的去极化(PAD) 传入以及这种控制是如何跟随周围神经而改变的 损伤。我们将检验以下假设： 1.节段性络脉和升络脉的突触效应 同一肌肉的传入可以由棘上选择性地控制 结构。我们将研究大脑皮质内和 大脑皮层和小脑皮质的表面阳极刺激 两条络脉在椎管内门槛上的延髓网状结构 位于中间核和/或运动核的同一传入纤维 另一种在Clarks氏柱或背侧柱核。 2.介导PAD的末级GABA能中间神经元包括At 至少两个功能截然不同的神经元亚群。实验 将被用来a)建立突触(GABA能)性质 椎管内分级微刺激产生的单突触垫 同一肌肉传入纤维的一条或两条侧支，以及b) 描述作用于最后一阶的分段输入和降序输入 脊髓内激活的GABA能中间神经元 微刺激。 3.粉碎后产生的焊盘图案的变化 周围神经仅限于受损的传入纤维。我们有 研究表明，刺激延髓网状结构(RF)会产生非常多的 小垫子在完整的肌梭传入中。然而，1-3个月后 周围神经挤压，射频刺激在传入产生较大的PAD 纤维与肌梭重新连接。这些变化的选择性 将通过记录至少两个不同的引出的垫子进行测试 外侧和内侧(MG)的下行输入(网状和皮质脊髓) 腓肠肌在只有MG神经的准备中传入 在1-3个月前就被粉碎了。我们还将检查是否在以下位置生产的衬垫 这段时间与突触前抑制有关。 4.PAD介导的中间神经元和中间核 介导非互易抑制的中间神经元与 背侧hon神经元的不同亚群。以前的工作已经表明 中间核至少有两个亚群 中间神经元介导非互惠的抑制作用。其中一人 仅产生突触后甘氨酸能抑制，而其他前和 突触后GABA能抑制。通过记录椎管内的视野 与单个中间神经元的活动相关的电位和 这些势与由下列因素产生的势之间的相互作用 节段性和下行通路的刺激，我们将能够 揭示单个中间神经元与神经元之间的功能关系 其他组的脊髓神经元。

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 vertebrate spinal cord and the role played by presynaptic inhibition in sensory-motor integration. The proposed experiments are aimed to disclose the selectivity of the supraspinal control exerted on the spinal pathways mediating the primary afferent depolarization (PAD) of individual muscle spindle and tendon organ afferents and how this control is modified following a peripheral nerve lesions. The following hypothesis will be tested: 1. The synaptic effectiveness of the segmental and ascending collaterals of the same muscle afferent can be selectively controlled by supraspinal structures. We will examine the effects produced by intracortical and surface anodal stimulation of the cerebral and cerebellar cortex and of the bulbar reticular formation on the intraspinal threshold of two collaterals of the same afferent fiber, one in the intermediate and/or motor nucleus and the other in Clarks's column or in the dorsal column nuclei. 2. The last-order GABAergic interneurons that mediate PAD comprise at least two functionally distinct subpopulations of neurons. Experiments will be made to a) establish the synaptic (GABAergic) nature of the monosynaptic PAD produced by graded intraspinal microstimulation either in one or in two collaterals of the same muscle afferent fiber, and b) to characterize the segmental and descending inputs acting on the last-order GABAergic interneurons that are activated by the intraspinal microstimulation. 3. The changes in PAD patterns that are produced after crushing a peripheral nerve are restricted to the lesioned afferent fibers. We have shown that stimulation of the bulbar reticular formation (RF) produces very little PAD in intact muscle spindle afferents. However, 1-3 months after a peripheral nerve crush., RF stimulation produces large PAD in afferent fibers reconnected with muscle spindles. The selectivity of these changes will be tested by recording the PAD elicited by at least two different descending inputs (reticulo- and cortico-spinal) on lateral and medial (MG) gastrocnemius afferents in preparations in which only the MG nerve was crushed 1-3 months previously. We will also examine if the PAD produced at that time is associated with presynaptic inhibition. 4. The PAD-mediating interneurons and the intermediate nucleus interneurons mediating the nonreciprocal inhibition are associated with different subpopulations of dorsal hon neurons. Previous work has shown that there are at least two subpopulations of intermediate nucleus interneurons mediating non-reciprocal inhibitory actions. One of them produces only postsynaptic glycinergic inhibition and the other pre- and postsynaptic GABAergic inhibition. By recording the intraspinal field potentials that are associated to the activity of single interneurons and the interactions of these potentials with potentials produced by stimulation of segmental and descending pathways, we will be able to disclose the functional relationship between individual interneurons and other sets of spinal neurons.