Simon M, Destombes J, Horcholle-Bossavit G, Thiesson D
Laboratoire de Physiologie et Biologie de la Motricité, CNRS URA 1448, Université René Descartes, UFR Biomédicale, Paris, France.
Neurosci Res. 1996 May;25(1):77-89. doi: 10.1016/0168-0102(96)01030-9.
Motoneurons innervating the peroneus brevis muscle of 1 week- and 3 week-old kittens were retrogradely labelled by HRP and examined by electron microscopy. At 1 week the distribution of mean cell body diameters was unimodal. Consequently alpha- and gamma-motoneurons could not be identified by their size. The aim of this study was to see whether the alpha- and gamma-motoneurons of kittens could be identified using the combination of ultrastructural criteria previously defined in the adult cat. Using these three criteria it was not possible to distinguish all the motoneurons as either alpha- or gamma in the kitten and a fourth criterion (frequency of F bouton profiles) was added to aid identification. However, with these four criteria, at 1 week six of 21 motoneurons and at 3 weeks two of 18 could still not be clearly identified as alpha or gamma (four were tentatively considered to be gamma, and four could not be identified). The maturation of alpha-motoneurons between 1 week and the adult was accompanied by an increase in somatic membrane area and a significant decrease in the somatic packing density of F boutons. On gamma-motoneurons there was a decrease in the somatic packing density of F boutons between 1 and 3 weeks. However, the numbers of F and S boutons remained stable for both motoneuron types. Age-related changes in apposition and active zone lengths of F and S boutons characterize the synaptic rearrangements which are occurring during the postnatal development of motoneurons.
用辣根过氧化物酶（HRP）对1周龄和3周龄小猫的支配腓骨短肌的运动神经元进行逆行标记，并通过电子显微镜检查。在1周龄时，平均细胞体直径的分布是单峰的。因此，无法通过大小来区分α运动神经元和γ运动神经元。本研究的目的是看看是否可以使用先前在成年猫中定义的超微结构标准的组合来识别小猫的α运动神经元和γ运动神经元。使用这三个标准，在小猫中无法将所有运动神经元区分为α或γ运动神经元，因此添加了第四个标准（F型终扣轮廓的频率）来辅助识别。然而，使用这四个标准，在1周龄时，21个运动神经元中有6个，在3周龄时，18个运动神经元中有2个仍无法明确识别为α或γ运动神经元（4个暂时被认为是γ运动神经元，4个无法识别）。1周龄至成年期α运动神经元的成熟伴随着体细胞表面积的增加和F型终扣体细胞堆积密度的显著降低。在γ运动神经元上，1至3周龄之间F型终扣的体细胞堆积密度有所降低。然而，两种运动神经元类型的F型和S型终扣数量保持稳定。F型和S型终扣的并置和活性区长度的年龄相关变化是运动神经元出生后发育过程中发生的突触重排的特征。
