Journals of Gerontology Series A: Biological Sciences and Medical Sciences, Vol 53, Issue 5 B369-B379, Copyright © 1998 by The Gerontological Society of America
Decreased axosomatic input to motoneurons and astrogliosis in the spinal cord of aged rats
S Kullberg, V Ramirez-Leon, H Johnson and B Ulfhake
Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
An increasing body of evidence indicates that aging-related impairments of
nervous functions are caused by damage to neuron integrity rather than by
loss of neurons. By using electron microscopy, we have examined axosomatic
boutons on spinal cord motoneurons derived from aged and young adult
Sprague-Dawley rats. The main finding was that about half of the examined
motoneuron somata from aged rats had a reduced (50%) bouton coverage, which
seemed to be caused by a smaller number of axosomatic bouton profiles. Long
stretches of the cell body plasma membrane were apposed by pale processes,
and immunolabeling for glial fibrillary acidic protein (GFAP) disclosed
that a number of the aged motoneurons appeared embedded in GFAP
immunopositive processes. Lumbar motoneurons seemed to be more severely
affected than cervical motoneurons. At the ultrastructural level, affected
motoneurons disclosed plasma membrane irregularities with
appendages/sprout-like extensions that in some cases were sites for
axosomatic contacts.
