Local circuit properties underlying cortical reorganization
Local circuit properties underlying cortical reorganization
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DOI：
10.1152/jn.00994.2001
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发表时间：
2002-09-01
影响因子：
2.5
通讯作者：
Merzenich, MM
中科院分区：
文献类型：
--
作者：
Hickmott, PW;Merzenich, MM
外周去神经支配已被证明会导致初级躯体感觉皮层（S1）中的去传入躯体位置区域的重组。然而，重组所依据的基本机制并没有得到很好的理解。在本文所述的实验中，一种新的在体内/体外制备的成年大鼠S1被用来确定与大鼠S1的皮质代表的去神经诱导的可塑性相关的局部电路特性的变化。在本研究中，大鼠S1的传入神经阻滞诱导切断桡神经和正中神经在前肢的成年大鼠，导致在一个快速移动的前爪/下颌边界的位置，移动量增加的时间分析，通过28天后去神经支配。两个边界的位置（即，原始的和重组的）用活体染料标记，并且来自标记区域的切片用于全细胞记录。反应诱发使用电刺激的颗粒上S1和记录在颗粒上神经元接近原始或重组的边界。对于每一个神经元，突触后电位（PSP）引起的刺激的纤维越过边界网站（CB刺激）和等效的刺激，没有交叉（NCB刺激）。用15 μ M CNQX加100 μ M DL-APV阻断兴奋性传递后，还检测了单突触抑制性突触后电位（IPSP）。比较CB和NCB刺激之间的PSP和IPSP的幅度，以量化边界部位对兴奋和抑制的影响。先前在正常（即，无诱导可塑性）大鼠S1表明，在正常边界，CB刺激诱发的PSP和IPSP均小于NCB刺激。对于去神经支配的大多数持续时间，类似的偏差（即，在新重组边界的位点处观察到PSP和IPSP的较小反应（CB刺激），而在抑制的原始边界位点处没有观察到这种偏差。因此，局部回路特性（兴奋和抑制）的变化可以反映皮层组织的更大范围的变化。然而，也观察到这些局部电路特性和在去神经支配的某些持续时间的新边界的存在之间的特定解离，这表明随着时间的推移，有几个皮质内过程有助于皮质重组，并且兴奋和抑制可能对它们有不同的贡献。
Peripheral denervation has been shown to cause reorganization of the deafferented somatotopic region in primary somatosensory cortex (S1). However, the basic mechanisms that underlie reorganization are not well understood. In the experiments described in this paper, a novel in vivo/in vitro preparation of adult rat S1 was used to determine changes in local circuit properties associated with the denervation-induced plasticity of the cortical representation in rat S1. In the present studies, deafferentation of rat S1 was induced by cutting the radial and median nerves in the forelimb of adult rats, resulting in a rapid shift of the location of the forepaw/lower jaw border; the amount of the shift increased over the times assayed, through 28 days after denervation. The locations of both borders (i.e., original and reorganized) were marked with vital dyes, and slices from the marked region were used for whole-cell recording. Responses were evoked using electrical stimulation of supragranular S1 and recorded in supragranular neurons close to either the original or reorganized border. For each neuron, postsynaptic potentials (PSPs) were evoked by stimulation of fibers that crossed the border site (CB stim) and by equivalent stimulation that did not cross (NCB stim). Monosynaptic inhibitory postsynaptic potentials (IPSPs) were also examined after blocking excitatory transmission with 15 muM CNQX plus 100 muM DL-APV. The amplitudes of PSPs and IPSPs were compared between CB and NCB stimulation to quantify effects of the border sites on excitation and inhibition. Previous results using this preparation in the normal (i.e., without induced plasticity) rat S1 demonstrated that at a normal border both PSPs and IPSPs were smaller when evoked with CB stimulation than with NCB stimulation. For most durations of denervation, a similar bias (i.e., smaller responses with CB stimulation) for PSPs and IPSPs was observed at the site of the novel reorganized border, while no such bias was observed at the suppressed original border site. Thus changes in local circuit properties (excitation and inhibition) can reflect larger-scale changes in cortical organization. However, specific dissociations between these local circuit properties and the presence of the novel border at certain durations of denervation were also observed, suggesting that there are several intracortical processes contributing to cortical reorganization over time and that excitation and inhibition may contribute differentially to them.