Hashizume K, Kanda K
Department of Central Nervous System, Tokyo Metropolitan Institute of Gerontology, Japan.
Neurosci Res. 1995 May;22(2):189-96. doi: 10.1016/0168-0102(95)00889-3.
We examined the number and size of ulnar (forelimb) and medial gastrocnemius (MG, hindlimb) motoneurons in middle-aged (9 months of age) and aged (27 months of age) male Fischer 344 rats. Morphological properties of the ulnar and the MG nerves were also studied. No significant difference was found in the mean number of the ulnar motoneurons between the two age groups, while that of MG motoneurons was significantly less in aged animals. A decrease in the number of myelinated fibers (including both afferent and efferent fibers) in the ulnar nerves was less than that in the MG nerves, although the age difference was not significant in either of the nerves. Soma atrophy of aged motoneurons was found in both MG and ulnar motor nuclei. The mean fascicular areas and myelinated fiber diameters were significantly increased in both the MG and the ulnar nerves in aged rats, but these were less pronounced for the ulnar nerve. The results indicate that most ulnar motoneurons, unlike MG motoneurons, survive at least to the age of 27 months. Morphological changes in the peripheral nerves were also less for the ulnar nerve than for the MG nerve. Thus, we conclude that the effects of aging on motoneurons and peripheral nerves innervating MG muscle of the hindlimb are greater than those innervating forelimb muscles.
我们研究了中年（9月龄）和老年（27月龄）雄性Fischer 344大鼠尺神经（前肢）和腓肠内侧肌神经（MG，后肢）运动神经元的数量和大小。还研究了尺神经和MG神经的形态学特性。两个年龄组的尺神经运动神经元平均数量没有显著差异，而老年动物的MG运动神经元数量显著减少。尺神经中髓鞘纤维（包括传入和传出纤维）数量的减少小于MG神经，尽管两条神经的年龄差异均不显著。在MG和尺神经运动核中均发现老年运动神经元的胞体萎缩。老年大鼠的MG神经和尺神经的平均束面积和髓鞘纤维直径均显著增加，但尺神经的变化不太明显。结果表明，与MG运动神经元不同，大多数尺神经运动神经元至少存活到27月龄。尺神经周围神经的形态学变化也比MG神经少。因此，我们得出结论，衰老对支配后肢MG肌肉的运动神经元和周围神经的影响大于支配前肢肌肉的运动神经元和周围神经。
