Nerve terminal morphology in C57BL/6NNia mice at different ages.
The mammalian neuromuscular junction (NMJ) appears to undergo a dynamic remodeling process with advancing age. Previous studies suggest that the NMJ becomes progressively larger with age, to a greater degree in fast-twitch muscles than slow-twitch muscles. To better understand this process, quantitative morphometry was conducted on soleus and extensor digitorum longus (EDL) nerve terminals from C57BL/6NNia mice aged 4, 8, 10, 12, 18, 22, 24, and 32 months. Computer-aided morphometry of camera lucida drawings of aging nerve terminals indicated significant differences in the size and complexity of NMJs in both muscles between different age groups; however, there were no significant net trends with age. The magnitude and direction of the morphometric changes depended on the particular ages compared, and occurred to a greater degree in the EDL. This study is the first comprehensive morphometric study of C57BL/6NNia nerve terminals at so many ages. The results are similar to those obtained for the Fischer 344 rat, and support the hypothesis that nerve terminal remodeling is a dynamic process, not a progressive elaboration.
Andonian
M H
MH
Andrus Gerontology Center, University of Southern California, Los Angeles.
Fahim
M A
MA
D000375:Aging / Q000502:physiology*; D000818:Animals; D001835:Body Weight; D007091:Image Processing, Computer-Assisted; D051379:Mice; D008810:Mice, Inbred C57BL; D009132:Muscles / Q000294:innervation / Q000502:physiology; D009469:Neuromuscular Junction / Q000033:anatomy & histology*