Effect of spinal cord injury on urinary bladder spinal neural pathway: A retrograde transneuronal tracing study with pseudorabies virus

Objectives. To determinate the effect of acute and chronic spinal cord injury (SCI) resulting from thoracic cord transection on the urinary bladder spinal neural pathway. Methods. Seventy-six adult Sprague-Dawley rats were randomly divided into four groups, non-SCI (normal rats undergoing no surgical procedure except pseudorabies virus [PRV] injection), SCIb (SCI and PRV injected immediately after SCI), SCIc (SCI and PRV injected at 3 weeks after SCI), and SCId (SCI and PRV injected at 3 months after SCI). Transcardiac perfusion fixation was done at appropriate survival periods after PRV injection into the bladder wall tissue. Sections of the dorsal root ganglion, spinal cord, and brain were processed for visualization of the virus by the streptavidin-peroxidase immunohistochemical procedure. Results. The bladder weight of the non-SCI, SCIb, SCIc, SCId rats was 144 +/- 9 mg, 142 +/- 8 mg, 486 +/- 51 mg, and 656 +/- 69 mg, respectively. The time-ordered flow charts of PRV tracing were similar in the non-SCI and SCI rats. The cross-sectional area of the labeled dorsal root ganglion cell profiles increased significantly after SCI (P < 0.001): 593 +/- 40 mum(2), 588 +/- 39 mum(2), 815 +/- 53 mum(2), and 902 +/- 57 mum(2) in the non-SCI, SCIb, SCIc, SCId rats, respectively. The number of labeled cells in the dorsal horn in the L6 and S1 segments 3 days after PRV injection markedly increased in chronic SCI rats, as did the number of labeled motor neurons 4 days after injection. Conclusions. Acute and chronic SCI have no effect on the process of virus transneuronal transport below the level of the lesion. Subsequent to chronic SCI, reorganization of the micturition reflex pathways may occur. (C) 2003 Elsevier Inc.