TRIGEMINOTHALAMIC ORGANIZATION AND PLASTICITY

本应用程序中的实验将评估传入神经的作用 腹侧触觉相关神经元发育中的活动 大鼠丘脑后内侧核(VPM)。指导性假说 对于所有的实验来说，一般的传入活动和 活动子集、模式化活动(区分 彼此不同的传入子集)，可以具有非常不同的 对靶神经元发育的影响。l我们建议所有 传入活动可能促进轴突和神经元的存活和发育。 一组给定神经元的树枝。相反，图案化的 传入活动可能是神经元轴突之间竞争所必需的。 有问题的神经元指向它们的目标，它可能会促进细胞死亡和 轴突回缩，可能还有树枝状乔木。我们将对此进行测试 通过操纵VPM神经元的传入活动来进行假说。我们会 应用河豚毒素降低这些细胞的所有传入活动 (TTX)至眶下神经(供血的三叉神经支 触须毛囊)，用于生命的前3周。我们只会减少 通过简单地粘合肌轴的方式来识别传入活动 在这同一时期，大家一起触动身体。我们将评估这些措施的影响 这些操作通过：1)对VPM细胞进行计数，2)确定受体 VPM神经元的场特征和树突形态 细胞内记录和注射辣根过氧化物酶(HRP)，以及3) Small标记的VPM细胞皮质轴突的重建 四季豆亮氨酸凝集素的丘脑沉积。 如果模式传入活动对一组神经的影响 细胞是该活动在轴突竞争中所起作用的函数 在他们的目标上有问题的神经元，应该可以模仿 通过阻断VPM细胞的损失模式传入输入的影响 它们的轴突在皮质中的活动。我们将通过应用TTX实现这一点 在生命的前3周到躯体感觉皮质，然后 评估以上列出的因变量。 在最后一系列研究中，我们将使用简单的细胞计数和 顺行和逆行运输Di-I确定两者的数目 VPM细胞和这些神经元及其轴突的形态特征 在新生大鼠身上。这将定义此部分的状态 当我们开始我们的操控时，我们的体感系统。这个 建立这一“基线”将有助于解释 前述各段概述的研究。

The experiments in this application will assess the role of afferent activity in the development of vibrissa-related neurons in the ventral posteromedial nucleus (VPM) of the rat's thalamus. The guiding hypothesis for all of the experiments is that afferent activity in general and a subset of that activity, patterned activity (activity that distinguishes distinct subsets of afferents from each other), may have very different effects upon the development of target neurons.l We suggest that all afferent activity may promote both survival and elaboration of axonal and dendritic arbors for a given population of neurons. Conversely, patterned afferent activity may be required for competition among the axons of the neurons in question at their target and it may promote cell death and the retraction of axonal and perhaps also dendritic arbors. We will test this hypothesis by manipulating the afferent activity to VPM neurons. We will reduce all afferent activity to these cells by application of tetrodotoxin (TTX) to the infraorbital nerve (the trigeminal branch that supplies the vibrissa follicles) for the first 3 weeks of life. We will reduce only patterned afferent activity by simply gluing the shafts of the mystacial vibrissae together for this same period. We will assess the effects of these manipulations by: 1) counting VPM cells, 2) determining the receptive field characteristics and dendritic morphology of VPM neurons via intracellular recording and horseradish peroxidase (HRP) injection, and 3) reconstructing the cortical axon arbors of VPM cells labeled by small thalamic deposits of Phaseolus vulgaris leucoagglutinin. If the effects of patterned afferent activity upon a population of nerve cells are a function of that activity's role in competition among the axons of the neurons in question at their target, it should be possible to mimic the effects of a loss patterned afferent input to VPM cells by blocking the activity of their axons in cortex. We will accomplish this by applying TTX to the somatosensory cortex for the first 3 weeks of life and then assessing the dependent variables listed above. In a final series of studies, we will use simple cell counting and anterograde and retrograde transport of Di-I to determine both the number of VPM cells and morphological properties of these neurons and their axons in newborn rats. This will define the status of this portion of the somatosensory system at the time when we initiate our manipulations. The establishment of this "baseline" will aid interpreting the results of the studies outlined in the preceding paragraphs.