De La Roza C, Reinoso-Suárez F
Departamento de Morfología, Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain.
J Comp Neurol. 2000 Nov 6;427(1):31-53. doi: 10.1002/1096-9861(20001106)427:1<31::aid-cne3>3.0.co;2-t.
In an attempt to contribute to the current knowledge of the brainstem reticular formation synaptic organization, the ultrastructure and distribution of synaptic terminal profiles on neurons in the ventral part of the oral pontine reticular nucleus (vRPO), the rapid eye movement (REM) sleep-induction site, were studied quantitatively. Terminals with asymmetric contacts and rounded vesicles were classified according to vesicle density as type I or II (high or low density, respectively). The area, apposed perimeter length, and mitochondrial area of type I terminals, on average, were significantly smaller than those of type II terminals. Type III and IV terminals had symmetric contacts and oval and/or flattened vesicles; type III terminals formed synapses between them and on initial axons. Type V and VI terminals showed characteristics intermediate to those of asymmetric and symmetric synapses. Interestingly, some terminal features were related to both terminal area and postsynaptic dendritic diameter. The percentages of different synapses sampled on somata were as follows: asymmetric synapses (usually formed by type II terminals; mean +/- S.D.), 26.4% +/- 3%; symmetric synapses, 46.7% +/- 5.2%; and intermediate synapses, 26.9% +/- 6.1%. The percentages of different synapses sampled on dendrites were asymmetric synapses, 62.1% +/- 9%; symmetric synapses, 25.6% +/- 8.1%; and intermediate synapses, 12.3% +/- 1.7%. Comparison between large- and small-diameter dendrites revealed that the percentages of symmetric synapses and type II terminals decreased, whereas the percentages of type I terminals increased as postsynaptic dendritic diameters became smaller. Synaptic density was approximately four times lower on somata than on dendrites. The vRPO synaptic organization reflects some patterns that are similar to those found in other regions of the central nervous system as well as specific synaptic patterns that are probably related to its functions: the generation and maintenance of REM sleep and the control of eye movement or limb muscle tone.
为了增进对脑干网状结构突触组织的现有认识，我们对作为快速眼动（REM）睡眠诱导位点的脑桥嘴侧网状核腹侧部（vRPO）神经元上突触终末轮廓的超微结构和分布进行了定量研究。具有不对称接触和圆形囊泡的终末根据囊泡密度分为I型或II型（分别为高密度或低密度）。I型终末的面积、贴合周长和线粒体面积平均显著小于II型终末。III型和IV型终末具有对称接触以及椭圆形和/或扁平囊泡；III型终末在它们之间以及初始轴突上形成突触。V型和VI型终末表现出介于不对称和对称突触特征之间的特征。有趣的是，一些终末特征与终末面积和突触后树突直径都有关。在胞体上采样的不同突触的百分比分别为：不对称突触（通常由II型终末形成；平均值±标准差），26.4%±3%；对称突触，46.7%±5.2%；中间型突触，26.9%±6.1%。在树突上采样的不同突触的百分比分别为：不对称突触，62.1%±9%；对称突触, 25.6%±8.1%；中间型突触，12.3%±1.7%。大直径和小直径树突之间的比较显示，随着突触后树突直径变小, 对称突触和II型终末的百分比降低，而I型终末的百分比增加。胞体上的突触密度比树突上大约低四倍。vRPO的突触组织反映了一些与中枢神经系统其他区域相似的模式以及可能与其功能相关的特定突触模式：REM睡眠的产生和维持以及眼球运动或肢体肌肉张力的控制。
