AGE-RELATED-CHANGES IN SOMA SIZE OF NEURONS IN THE SPINAL-CORD MOTOR COLUMN OF THE CAT

The present study was undertaken to examine the effect of the aging pr ocess on the soma size and number of motoneurons and interneurons in t he motor column of the spinal cord of old cats. Neurons in the motor c olumn were divided into small and large populations based on a bimodal distribution of their soma cross-sectional areas. A 17% decrease in t he cross-sectional area of small neurons was observed, this decrease w as statistically significant (P < 0.0001). The cross-sectional area of large neurons decreased by only 6%, which was statistically significa nt (P < 0.05). On the other hand, there was no significant difference in the number of large, small or of these combined population of ventr al horn neurons in the aged cats compared with the control animals. Th is data suggest that neurons in the motor column are not uniformly aff ected by the aging process because morphological changes are proportio nally greater in small neurons than in large neurons.