age-associated changes on axonal regeneration and functional outcome after spinal cord injury in rats.

this study was conducted to evaluate the association between aging and regenerative potential of spinal cord injury. three groups of male sprague-dawley rats, including young (40 days), mature (5-6 months) and old (28-29 months) were spinally hemisected at the l1 level. the locomotor performance was assessed weekly for eight weeks after lesion using locomotors' rating scale developed by basso, bresnahan and beattie (bbb). in the tracing study, retrograde labeled neuron was counted in the lateral vestibular nucleus for axonal regeneration. from 4-8 weeks, the functional recovery of the young and mature age rats was significantly increased in comparison to the old age group. at 8 weeks, young and mature animals achieved a plateau score of (mean ± sd), 17 ± 1.47 and 16.8 ± 0.70 respectively, and the old rats reached an average score of 13.8±1.63 (p<0.05). the mean number of labeled neurons in the vestibular nucleus in the young group (mean ± sd): 32.05 ± 1.03 increase significantly compared to the older age group 5.01 ± 1.31 (p<0.05). current findings suggest that axonal repair and functional improvement decrease in aged animals after partial spinal cord injury. thus, the aging process may affect the regenerative capacity of the injured central nervous system, and axonal regeneration is age dependent.