AGE-CHANGES IN THE TIBIAL AND PLANTAR NERVES OF THE RAT

  • 1 January 1980
    • journal article
    • research article
    • Vol. 130  (MAR) , 417-428
Abstract
The changes in the myelinated fibers of the tibial and plantar nerves, in rats, 2-24 mo. of age, were observed. There is an initial early increase in fiber diameter followed by a later more gradual increase, which ceases after approximately 9 mo. of age in the tibial nerve but continues longer in the medial plantar nerve. The fiber size distribution remains substantially unimodal. In both nerves maximal and average fiber diameter become reduced by 24 mo. Total fiber number shows considerable variability between animals, but no definite systematic alteration with age is detectable. Teased fiber preparations demonstrate a low level of abnormality in the tibial nerve until after 18 mo. of age, but by 24 mo. approximately 30% of fibers display abnormalities. Although paranodal and segmental demyelination and remyelination, and axonal degeneration and regeneration occur, the latter type of change predominates. In the lateral plantar nerve, paranodal and segmental demyelination become detectable to a significant extent from 6 mo. of age. Axonal degeneration and regeneration become evident after 15 mo. By 24 mo. of age, 55% of fibers show abnormalities. The changes in the plantar nerves probably represent a compression neuropathy; in the tibial nerves the cause of the changes is uncertain. Both these changes require consideration in experimental neuropathies.