Wall J T, Cusick C G, Migani-Wall S A, Wiley R G
Department of Psychology, Vanderbilt University, Nashville, Tennessee.
J Comp Neurol. 1988 Nov 22;277(4):578-92. doi: 10.1002/cne.902770410.
The present study was designed to assess whether cortical changes after peripheral nerve damage are related to the degree of death of primary sensory neurons in the damaged nerve. The cytotoxin ricin was injected into the sciatic nerves of adult rats to kill primary sensory neurons with axons through the injection site. Following periods of 6-101 days, the S-I hindpaw map was evaluated with neurophysiological techniques and compared with the hindpaw maps of previously studied normal adult rats and adult rats that had undergone adult or neonatal sciatic section at a comparable level of the nerve. These comparisons allowed evaluation of cortical functional organization following different degrees of sensory neuron loss after sciatic nerve injury. There were three main results. 1) The comparison of ricin-treated and normal adult rats indicated that ricin treatment interrupted inputs from the sciatic skin territory on the hindpaw and caused a limited increase in the size of the cortical area that was activated by stimulation of hindpaw skin innervated by the remaining saphenous nerve. 2) The cortical maps of rats that had undergone adult ricin treatment (relatively large primary neuron loss) or section during adulthood (small to moderate primary neuron loss) were similar. In both groups, only the saphenous hindpaw skin was represented in cortex, and the cortical area that was activated by stimulation of the saphenous hindpaw skin had undergone a comparable limited enlargement. 3) The comparison of ricin-treated adult rats (relatively large primary neuron loss) and adult rats that had undergone neonatal section (relatively large primary neuron loss) indicated that cortical organization differed after these treatments. In particular, after ricin treatment the cortical area that was activated by stimulation of the saphenous hindpaw skin was larger than the comparable area in neonatal denervates, and the topographical progressions between the hindpaw and adjacent body representations were not as variable as after neonatal section. These findings indicate that cortical maps are altered after injection of ricin into a nerve. The similarity in cortical organization after ricin treatment (relatively large sensory neuron loss) and nerve section in adults (relatively small sensory neuron loss) and the differences in cortical organization after ricin treatment and nerve section in neonates (both relatively large sensory neuron loss) indicate cortical changes do not covary as a simple function of the degree of peripheral neuron death.
本研究旨在评估外周神经损伤后皮质变化是否与受损神经中初级感觉神经元的死亡程度相关。将细胞毒素蓖麻毒素注射到成年大鼠的坐骨神经中，以杀死通过注射部位具有轴突的初级感觉神经元。在6 - 101天的时间段后，用神经生理学技术评估S - I后爪图谱，并与先前研究的正常成年大鼠以及在神经的可比水平进行成年或新生坐骨神经切断的成年大鼠的后爪图谱进行比较。这些比较使得能够评估坐骨神经损伤后不同程度的感觉神经元丧失后的皮质功能组织。有三个主要结果。1）蓖麻毒素处理的成年大鼠与正常成年大鼠的比较表明，蓖麻毒素处理中断了来自后爪坐骨皮肤区域的输入，并导致由剩余隐神经支配的后爪皮肤刺激所激活的皮质区域大小有限增加。2）接受成年蓖麻毒素处理（相对较大的初级神经元丧失）或成年期切断（小到中度的初级神经元丧失）的大鼠的皮质图谱相似。在两组中，皮质中仅代表隐神经后爪皮肤，并且由隐神经后爪皮肤刺激所激活的皮质区域经历了可比的有限扩大。3）蓖麻毒素处理的成年大鼠（相对较大的初级神经元丧失）与接受新生期切断的成年大鼠（相对较大的初级神经元丧失）的比较表明，这些处理后皮质组织不同。特别是，蓖麻毒素处理后，由隐神经后爪皮肤刺激所激活的皮质区域大于新生去神经支配大鼠中的可比区域，并且后爪与相邻身体代表之间的地形进展不像新生期切断后那样多变。这些发现表明，将蓖麻毒素注射到神经中后皮质图谱会发生改变。蓖麻毒素处理后（相对较大的感觉神经元丧失）和成年期神经切断后（相对较小的感觉神经元丧失）皮质组织的相似性，以及蓖麻毒素处理和新生期神经切断后（两者均为相对较大的感觉神经元丧失）皮质组织的差异表明，皮质变化并非作为外周神经元死亡程度的简单函数而协同变化。
