Lower urinary tract function in spinal cord-injured rats: midthoracic contusion versus transection

To compare changes in lower urinary tract (LUT) function with modifications in pathways that regulate LUT function using two different animal models (incomplete and complete) of spinal cord injury (SCI).

Female Sprague-Dawley rats were used. SCI was made at Th8/9 by a contusion injury (contusion, n=9) or a complete transection (transection, n=9). Unoperated rats were used as normal controls (normal, n=6). LUT function was evaluated by micturition behavior in metabolic cages for 24 h and cystometry in awake animals. Immunocytochemical staining at the L6 spinal cord, spinal areas associated with LUT, was performed to identify descending modulatory fibers and dorsal root afferents that project to the L6 spinal cord.

Volume/micturition in metabolic cages gradually increased in both contusion and transection groups compared with normals, and operated groups did not differ from each other. Urodynamic parameters from cystometry were significantly different in contusion and transection groups compared with normals, but again there was no significant difference between contusion and transection groups. Immunocytochemical analyses at the L6 spinal cord showed no serotonergic or noradrenergic fibers in transection group, but some descending fibers remained in contusion group, indicating sparing. Small dorsal root afferents were denser in both contusion and transection groups than in normals, indicating sprouting.

Although differences were not found in LUT function in operated animals, supraspinal and dorsal root projections to the L6 spinal cord responded differently to contusion and transection. This suggests that the benefits of pharmacologic treatments may be different in two lesion models.