Journal of Neurophysiology, Vol 53, Issue 6 1582-1589, Copyright © 1985 by APS
Effects of chronic stress and exercise on age-related changes in end-plate architecture
J. L. Rosenheimer
The effects of chronic stress (foot shock) or stress coupled with exercise
(treadmill running) on age-related changes in nerve terminal branch number
per end plate were examined in three physiologically different muscles, the
diaphragm and two hindlimb muscles, the extensor digitorum longus (EDL),
and the soleus, from 24- to 25-mo rats. End-plate structure was examined by
use of a silver-gold impregnation of the axon and its terminal arborization
and was compared with similar data obtained from 10- and 25-mo sedentary
control animals. Stress from foot shock resulted in decreases of 30 and
23%, which are significant at the 0.05 level, in the mean number of nerve
terminal branches per end plate in the fast-twitch EDL and diaphragm of
25-mo rats, respectively; a similar, but less dramatic decline in branch
number was observed in the end plates of the slow-twitch soleus. Exercise
superimposed on foot shock counteracted the decrease in branch number
resulting from foot shock alone in the hindlimb muscles; in contrast,
terminal branch number within the diaphragm end plates declined an
additional 29% in the exercised group. Exercise plus shocking eliminated
the significant age-related decrease in branch number in the soleus between
the 10- and 25-mo animals; however, it produced a significant decrease in
the diaphragm of the 25-mo compared with the 10-mo animals. There was a
significant increase in the occurrence of sprouting nerve terminals in the
EDL and soleus of exercise-shocked animals compared with 25-mo controls,
thus counteracting the age-related decrease observed in the 25-mo compared
with 10-mo control animals.(ABSTRACT TRUNCATED AT 250 WORDS)
