部分去传入猫脊髓背核突触性终末的可塑性变化——电镜定量研究

PLASTICITY OF SYNAPTIC TERMINALSIN CLARKE'S NUCLEUS OF SPINAL CORD AFTER PARTIAL DEAFFERENTATION IN ADULT CAT——QUANTITATIVE ELECTRON MICROSCOPIC STUDY

本实验用猫单侧后肢背根备用模型(切断L_1-L_5、L_7-S_2背根,保留L_6背根),应用光镜体视学计量分析背核和背核神经毡的横切面积;电镜定量研究背核神经毡内三种突触性终末的数量变化。结果显示:实验侧L_3背核及背核神经毡的横切面积未因去传入而发生皱缩;实验侧单位面积内突触性终末总数和活性带数量保持不变,其中来源于背根的巨大终末数还保留对照侧的75%,而来源于L_4以下脊髓中间神经元的小扣型终末数增加了70%;上述两类含圆形小泡的终末总数保持不变;来源于背核边缘细胞的扁平小泡终末数与列照侧无显著性差异。上述结果表明去大部分后肢背根后,在背核内引起了备用背根(L_6)的同型出芽和其它来源轴突的异型出芽,并重建了突触联系。因而从数量上完全代偿了丢失的终末。

Cats received unilateral lumbosacral dorsal rhizotomy from L1 to S2 with sparing of L6, Morphometrical method was used for analysis of the area changes of the Clarke's nucleus as well as neuropil caused by deafferentation. The numerical changes of the three types of synaptic terminals in Clarke's nucleus were detected by electron microscopy. The results were as follows: No statistically significant atrophy of the area of Clarke's nuc'eus and neuropil was found in the rhizotomy side. Total number of synaptic terminals or active zones of synapses in rhizotomy side remained normal, and the amount of giant axonal terminals(GAT)originating from dorsal roots was reduced to 75 percent, while the small bouton terminals(SBT)originating from interneurons below L4 were increased by 70 percent as compared with that of the control side. The total number of synaptic terminals containing spheric vesicles including GAT and SBT showed little difference in comparison with the control side. Number of flat vesicle terminals originating from bordor cell of the Clarke's nucleus displayed also no significant change. All these findings indicate that deafferentation of most dorsal roots of cat hind limb could induce both homotypie sprouting from spared roots and heterotypic sprouting from other sources, and new synaptic contacts are also formed. Therefore, the complete replacement of synapse in amount is resulted.