Warren R, Tremblay N, Dykes R W
Department of Neurology, McGill University, Montreal, Quebec, Canada.
J Comp Neurol. 1989 Oct 22;288(4):583-92. doi: 10.1002/cne.902880405.
Somatosensory cortex reorganizes following restricted deafferentation so that deprived neurons acquire new receptive fields. Electrophysiological data suggest that a decrease in inhibition might be one of the mechanisms contributing to these changes. This hypothesis was tested by evaluating quantitatively glutamic acid decarboxylase (GAD) immunoreactivity and cytochrome oxidase (CO) activity in normal and partially deafferented rat hindlimb somatosensory cortex. In normal animals, there were laminar differences in the frequencies of GAD+ cells that correlated with the levels of CO activity. Two weeks after transection of the sciatic nerve, CO levels were reduced in all layers of the hindlimb somatosensory cortex contralateral to the nerve transection whereas the frequencies of GAD+ cells were unchanged except in layer IV where a 16% decrease was observed. This observation is consistent with the hypothesis that the expression of GAD in layer IV is partially controlled by the amount of afferent input. The ability of novel inputs to develop stable patterns of excitation in deafferented somatosensory cortex may depend upon the reduction of GABAergic inhibition which follows deafferentation.
体感皮层在局限性传入神经阻滞之后会发生重组，从而使失去传入神经支配的神经元获得新的感受野。电生理数据表明，抑制作用的减弱可能是促成这些变化的机制之一。通过定量评估正常和部分传入神经阻滞大鼠后肢体感皮层中谷氨酸脱羧酶（GAD）免疫反应性和细胞色素氧化酶（CO）活性，对这一假说进行了验证。在正常动物中，GAD阳性细胞的频率存在层状差异，这与CO活性水平相关。坐骨神经横断两周后，与神经横断对侧的后肢体感皮层各层CO水平均降低，而GAD阳性细胞的频率除IV层外均未改变，IV层观察到下降了16%。这一观察结果与IV层中GAD的表达部分受传入输入量控制的假说一致。新输入在去传入体感皮层中形成稳定兴奋模式的能力可能取决于去传入后GABA能抑制作用的减弱。
