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KMID : 0378019870300080037
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New Medical Journal
1987 Volume.30 No. 8 p.37 ~ p.43
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Changes in Axonal Numbers and Diameters of the Trochlear Nerve in Old Rat
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Abstract
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Morphornetric analysis of senile changes in trochlear nerve was studied by electron microscopy. Four normal young adults (3-5 months) and five old animals (18-22 months) were examined.
The mean number of unmyelinated axons decreases from 60 in young adults to 45 in old animals.
The myelinated axons are distinguished easily into two kinds, small and large, and their size distribution shows bimodal figure. The small myelinated axons average 65 in young adults and about the same number in old animals, but the large myelinated axons decrease from 218 in average in young adults to 187 in average in old animals.
The mean diameter of small myelinated axons is slightly increased and conversely that of large myelinated axons is decreased slightly in old animals.
Therefore, on senile process, the unmyelinated axons which mostly serve as sympathetic fibers and the large myelinated axons known as motor fibers to the fast muscle fibers are first affected, but the small myelinated axons which serve as motor fibers to the slow muscle fibers or sensory fibers from stretch -sensitive mechanoreceptors are not.
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