ASSESSMENT OF LOWER URINARY-TRACT FUNCTIONAL DEFICIT IN RATS WITH CONTUSIVE SPINAL-CORD INJURY

Traumatic spinal cord injury (SCI) produces lower urinary tract (LUT) dysfunction that has been studied in surgical transection models. Our aim was to assess LUT functional deficit in a clinically relevant mode l of incomplete SCI to investigate how partial preservation of suprasp inal connections might affect LUT dysfunction. Standardized weight-dro p contusion (10 g x 2.5 cm) or complete transection, was produced at T 8 in female Sprague-Dawley rats. Behavioral tests were used to assess hind limb sensorimotor function at Day 1 after surgery and weekly ther eafter. The urometric experiments were conducted on groups (n = 7) of uninjured rats and on injured rats during Weeks 1 and 2 after SCI (bef ore and after spontaneous voiding was established) as well as Week 2 a fter a complete transection (n = 3), Under anesthesia, the bladder was continuously perfused with saline, Changes in bladder pressure and ex ternal urethral sphincter (EUS) electrical activity were monitored. Th e bladder was then dissected and weighed and both the bladder and spin al cord were fixed for pathoanatomical analyses. Our results indicate that several aspects of LUT dysfunction after contusive SCI were simil ar to transection, e.g., reduction of voiding efficiency (similar to 5 % of normal value), decrease in inter-contraction interval (47%), incr ease in bladder capacity (8-fold), and weight (4.6-fold), One aspect a ppeared different from transection-partial recovery from acute bladder /sphincter dyssynergia. Because the coordination of bladder and EUS fu nction is mediated by brainstem pathways, partial recovery of synergy after SCI was likely due to sparing of some relevant bulbospinal proje ctions as was confirmed by retrograde transneuronal viral tracing.