Observation of neuropeptides in bladder after spinal cord injury in rats

Abstract

To observe the altered expressions of neuropeptide Y, substance P and vasoactive intestinal peptide in detrusor of SD rats after spinal cord injury and explore the relationship of the above neuropeptides and neurogenic bladder after spine cord injury. Twenty male clean-grade SD rats, aged 6 weeks, were selected and randomized into spinal cord injury group (n = 10) and control group (n = 10). Rats in spinal cord injury group were smashed at T10 to cause spinal cord incomplete injury model by the weight drop method while laminectomy alone without smashing was administered in control group. At Week 1 post-operation, all rats were assessed by the maximum bladder capacity, bladder compliance and detrusor pressure for the confirmation of spastic bladder. And all detrusor specimens were marked with argentation and immunohistochemistry for the analyses of nerve fibers, neuropeptide Y, substance P and vasoactive intestinal peptide. The results were evaluated with semiquantitative method to observe the contents of nerve fiber and neuropeptides. At Week 1 post-operation, the mean maximum bladder compactly, mean maximum detrusor pressure and mean compliance in SCI rats was 0.71 ± 0.24 ml, 32.27 ± 3.12 cm H2O and 0.020 ± 0.009 ml/cm H2O versus 2.0 ± 0.4 ml, 21.0 ± 3.0 cm H2O and 0.090 ± 0.020 ml/cm H2O in normal control group respectively. And the differences were statistically significant (P < 0.01). Meanwhile, the mean content of nerve fibers of neurogenic bladder decreased markedly than that of normal control group (2.58 ± 0.13 vs 5.65 ± 0.26). As compared with the normal control group, the expressions of neuropeptide Y, substance P and vasoactive intestinal peptide (mean integrated optical density: 3.2 ± 0.5, 1.7 ± 0.4 and 2.1 ± 0.4 respectively) decreased dramatically in SCI rats. And the differences were statistically significant (P < 0.01). The number of nerve fibers and the content of neuropeptides significantly decrease in neurogenic bladder after spinal cord injury in rats. The reduction of neuropeptides may be correlated with the formation of neurogenic bladder after spinal cord injury.