Abstract
BackgroundPrior studies have compared the effect of spinal cord injury elicited using distinct approaches on motor and visceral function. However, the impact of such discrete modes of injury specifically on bladder muscle contractility has not been explored in detail. The goal of this study is to compare the impact of complete spinal cord transection versus clip compression at thoracic vertebra eight (T8) on bladder muscle contractility.MethodsRats underwent no treatment (Control), laminectomy (Sham, SH); complete extradural transection (TX); or cord compression with an aneurysm clip (CX). Bladders and spinal cords were harvested at 6 wk for contractility studies or histological analysis.ResultsDetrusor strips from TX and CX rats showed higher spontaneous activity than those from SH rats. Furthermore, the duration of the neurally-mediated contractile response was longer in TX and CX rats compared to controls and showed attenuated relaxation. No significant differences were observed between muscle strips from SH, TX or CX rats in response to KCl, ATP or phenylephrine. However, tissues from TX and CX rats showed a higher sensitivity to carbachol compared to that from SH animals.ConclusionsComplete SCI in rats either by cord transection or compression elicits qualitatively similar changes in bladder muscle contractility. Whereas cord transection is arguably easier to perform experimentally, cord compression better models the situation observed clinically, such that each approach has clear advantages and limitations.
Highlights
Prior studies have compared the effect of spinal cord injury elicited using distinct approaches on motor and visceral function
Whereas many parameters relevant to voiding such as bladder capacity, voiding efficiency and micturition cycle time were indistinguishable between complete cord transection and cord compression [11,12], selected aspects of lower urinary tract function were different
In this study we have employed two modes of thoracic spinal cord injury to test the hypothesis that spinal cord injury following complete transection versus clip compression injury elicits distinct effects on bladder smooth muscle contractility
Summary
Prior studies have compared the effect of spinal cord injury elicited using distinct approaches on motor and visceral function. The goal of this study is to compare the impact of complete spinal cord transection versus clip compression at thoracic vertebra eight (T8) on bladder muscle contractility. In this study we have employed two modes of thoracic spinal cord injury to test the hypothesis that spinal cord injury following complete transection versus clip compression injury elicits distinct effects on bladder smooth muscle contractility. We have chosen thoracic vertebra 8 (T8) as the site of injury as this emulates the phenotype of an upper motor neuron lesion Injury at this level interrupts all major efferent and afferent pathways including corticospinal, rubrospinal, vestibulospinal, spinothalamic and spinocerebellar tracts. Suprasacral injury is effective in eliciting a phenotype comprising an overactive/reflex bladder
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