Does reorganization in the cuneate nucleus following neonatal forelimb amputation influence development of anomalous circuits within the somatosensory cortex?
Does reorganization in the cuneate nucleus following neonatal forelimb amputation influence development of anomalous circuits within the somatosensory cortex?
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DOI：
10.1152/jn.00867.2007
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发表时间：
2008-02-01
影响因子：
2.5
通讯作者：
Mooney, Richard D.
中科院分区：
文献类型：
--
作者：
Lane, Richard D.;Pluto, Charles P.;Mooney, Richard D.
新生大鼠切断前肢后，坐骨神经传入纤维发芽进入楔状核(CN)，40%的CN神经元同时表达前肢残端和后肢感受区。这些大鼠初级躯体感觉皮层(S-I区)的前肢-残端区包含第四层神经元，既表达残肢感受区，也表达后肢感受区。然而，异常输入的来源是S-I后肢区域，通过皮质内投射传递到S-I前肢残肢区域。虽然S-I的重组反映了大脑皮层回路的变化，但这些变化可能反过来依赖于CN的重组。本研究旨在直接检测在S-I前肢残肢野表达后肢传入是否需要将坐骨神经传入发芽入CN。为抑制神经发芽，神经营养因子-3(NT-3)应用于神经切断后。在P60或更老的时候，NT-3处理的大鼠在CN中显示最少的坐骨神经纤维。NT-3处理的截肢大鼠CN的多单位电生理记录显示，6.3%的部位同时有残肢/后肢反应，而生理盐水处理的截肢动物的这一比例为30.5%。对S-I受体阻断后的评价显示，NT-3处理的大鼠后肢反应部位占残肢代表的百分比(34.2%)与生理盐水处理的大鼠(31.5%)无显著差异。这些结果表明，在S-I前肢/残肢区域内，以坐骨神经传入发芽进入CN的形式的脑干重组不是后肢异常感受区发育所必需的。
Neonatal forelimb amputation in rats produces sprouting of sciatic nerve afferent fibers into the cuneate nucleus (CN) and results in 40% of individual CN neurons expressing both forelimb-stump and hindlimb receptive fields. The forelimb-stump region of primary somatosensory cortex (S-I) of these rats contains neurons in layer IV that express both stump and hindlimb receptive fields. However, the source of the aberrant input is the S-I hindlimb region conveyed to the S-I forelimb-stump region via intracortical projections. Although the reorganization in S-I reflects changes in cortical circuitry, it is possible that these in turn are dependent on the CN reorganization. The present study was designed to directly test whether the sprouting of sciatic afferents into the CN is required for expression of the hindlimb inputs in the S-I forelimb-stump field. To inhibit sprouting, neurotrophin-3 (NT-3) was applied to the cut nerves following amputation. At P60 or older, NT-3-treated rats showed minimal sciatic nerve fibers in the CN. Multiunit electrophysiological recordings in the CN of NT-3-treated, amputated rats revealed 6.3% of sites were both stump/hindlimb responsive, compared with 30.5% in saline-treated amputated animals. Evaluation of the S-I following GABA receptor blockade, revealed that the percentage of hindlimb responsive sites in the stump representation of the NT-3-treated rats (34.2%) was not significantly different from that in saline-treated rats (31.5%). These results indicate that brain stem reorganization in the form of sprouting of sciatic afferents into the CN is not necessary for development of anomalous hindlimb receptive fields within the S-I forelimb/stump region.