Chiaia N L, Bauer W R, Zhang S, King T A, Wright P C, Hobler S C, Freeman K A
Department of Anatomy, Medical College of Ohio, Toledo 43699.
J Comp Neurol. 1992 Dec 22;326(4):561-79. doi: 10.1002/cne.903260406.
The present study examined the way in which an indirect partial deafferentation of the medial portion of the ventrobasal complex (VPM/VPL) induced by neonatal transection of the infraorbital nerve (ION) altered the structural and functional properties of its constituent neurons. This manipulation significantly reduced the volume of the contralateral VPM/VPL. In addition, cell counts in Nissl-stained material revealed a significant reduction of the number of VPM/VPL neurons contralateral to neonatal ION transection. We also analyzed the effect of neonatal ION transection on the soma-dendritic morphology of individual neurons in the ventral posteromedial nucleus of the thalamus (VPM) by intracellular injection of horseradish peroxidase (HRP) in vivo and Lucifer yellow in fixed slices. Neonatal transection of the ION resulted in increased dendritic length, area, and volume of VPM neurons in both preparations; however only the changes observed in fixed slices reached statistical significance. Alterations in the functional characteristics of VPM neurons were also observed following neonatal nerve damage. There was a significant decrease in the percentage of vibrissae-sensitive neurons and a corresponding increase in the percentages of neurons responsive to guard hair deflection or that were unresponsive to peripheral stimulation. Neonatal nerve damage also resulted in significantly longer latencies of VPM cells after stimulation of either trigeminal nucleus principalis or subnucleus interpolaris. The present results indicate that the development of normal response properties and soma-dendritic morphology of VPM neurons is dependent upon intact afferent input during development. Indirect partial deafferentation of VPM/VPL by neonatal transection of the ION results in reduced neuron number, which may result in decreased competition among the dendrites of these neurons. This proposal is consistent with observations of increased dendritic dimensions of VPM neurons contralateral to neonatal ION damage.
本研究考察了通过新生期眶下神经（ION）横断诱导腹后内侧/腹后外侧复合体（VPM/VPL）内侧部分间接部分去传入的方式，如何改变其组成神经元的结构和功能特性。这种操作显著减小了对侧VPM/VPL的体积。此外，尼氏染色材料中的细胞计数显示，新生期ION横断对侧的VPM/VPL神经元数量显著减少。我们还通过在体胞内注射辣根过氧化物酶（HRP）以及在固定切片中注射荧光黄，分析了新生期ION横断对丘脑腹后内侧核（VPM）单个神经元胞体-树突形态的影响。新生期ION横断导致两种制备物中VPM神经元的树突长度、面积和体积增加；然而，只有在固定切片中观察到的变化具有统计学意义。新生期神经损伤后，VPM神经元的功能特性也发生了改变。对触须敏感的神经元百分比显著下降，而对触毛偏转有反应或对周围刺激无反应的神经元百分比相应增加。新生期神经损伤还导致在刺激三叉神经主核或极间亚核后，VPM细胞的潜伏期显著延长。目前的结果表明，VPM神经元正常反应特性和胞体-树突形态的发育依赖于发育过程中完整的传入输入。新生期ION横断导致VPM/VPL间接部分去传入，导致神经元数量减少，这可能导致这些神经元树突之间的竞争减少。这一观点与新生期ION损伤对侧VPM神经元树突尺寸增加的观察结果一致。
