The Effection Of Long-term Sacral Anterior Root Stimulation Of Anodal Block In Rabbit Neurogenic Bladder Function Reconstruct After Complete Spinal Cord Injury

Objective:To observer the effection of long-term sacral anterior root stimulation of anodal block in rabbit neurogenic bladder function reconstruction after complete spinal cord injury, explore the possible mechanism of recovery of bladder function.Methods:50 rabbits with no urodynamic abnormalities were randomized into sham operation group (A group,10 rats) and spinal cord injury group (B group,40 rats). The spinal cord injuried animals model was established by completely spinal occlusion. Urodynamic examination was performed after 2 weeks to appear detrusor hyperreflexia and detrusor sphincter dyssynergia as a diagnostic criteria for neurogenic bladder. Depending on whether implanted electrodes, the B group was divided into C group (neurogenic bladder group) and D group (anode block electrical stimulation group). Long-term electrical stimulation was used for D group, each stimulus time was 30 minutes,6 times a day for 4 weeks. After 4 weeks urodynamic testing was done again to assess the bladder function and using electron microscopy and immunohistochemical method to detect the expression of neurotransmitter receptors and nerve growth factor in the 3 groups of rabbits bladder detrusor. Electrical stimulation may be the possible mechanisms to improve bladder function.Results:1. Animal models and urodynamic examination:A group died 2 survived 8; B group(40 rabbits) died 6 mainly because urinary tract infection,3 excluded by model screening, the remaining was 31; After randomization again, C group 16, D group 15. C group died 7 during the feeding, survived 9. D group died 1,5 nerve root injury during implanted electrode.1 excluded because less reaction during the process of the electrical stimulation. A group of 8, C group of 9, D group of 8 rabbits were into the next experiment. In A group, the pressure curves in bladder filling phase were smooth before and after surgery, the reflex of voiding is existence, there was no detrusor contraction and no differences in the dynamic parameters. B group 2 weeks after the operation, the main features of urodynamics were that urinary bladder resting pressure was increased, detrusor leak point pressure was elevated and detrusor was hyperactivity during bladder filling (more is invalid contraction), detrusor-sphincter dyssynergia was occurred during voiding and decreased urine output, increased residual urine volume, bladder volume reduc-tion, decreased voiding efficiency and bladder compliance decreased. The urodynamic characteristics of electrical stimulation group after long-term electrical stimulation were increased resting bladder pressure and decreased detrusor leak point pressure. Moreover, the invalid detrusor contraction is reduced during bladder filling, sphincter electromyography was stable during urination, urine output increased, decreased residual urine, bladder volume increased, efficiency increased urination and bladder compliance increased.2. Electron microscopy:In normal group, the smooth muscle cells were lined up in order, oval-shaped nucleus, heterochromatin behind the nuclear envelope, the nucleolus clearly visible, more dense plaques and dense bodies in muscle mass, mitochondria and rough endoplasmic reticulum seen in the cells. Between the cells, a large number of intermediate junctions can be seen, occasionally interstitial collagen and elastic fibers. There were no abnormalities in the cell junctions, smooth muscles and intermediate junctions. While in the injury group, we found that detrusor cells disorder, size incosistant, increased apoptotic cells, staining chromatin condensation, nuclear membrane surface uneven, a nuclear pyknosis, increased smooth muscle cell organelles, vacuolization mitochondria, lysosomes, Golgi complex and rough endoplasmic reticulum swelling, widening the gap between cells, collagen fibers increased, cell protrusion connection, desmosomes and gap junctions increased, disordered filaments in smooth muscle cells, the accumulation of high electron density materials around cell membrane. In electrical stimulation group versus injury group, smooth muscle cells were in the rule, unifoum size, rare apoptotic cells, light colored chromatin, nuclear condensation disappears, reduced intracellular organelles swelling, shortened the gap between muscle cells, collagen fibers decreased and cell connections and gap junctions reduced.3. Immunohistochemistry:M2 receptor expression was increased in the injury group, located mainly in presynapse, smooth muscle and epithelium and electrical stimulation can reduce it. After long-term injury M3 receptor stain was weakened in muscle cells, but in interstitial cells the expression is still strong. After long-term electrical stimulation, staining was increased in muscle cells but reduced even to normal in interstitial cells;β2-AR were mainly located in epithelial cells of the bladder and detrusor cells. The expression of it was decreased after the long-term injury,but increased after electrical stimulation; P2X3 receptors were increased significantly under epithelium and intercellular substance after injuried. Its expression was increased on the bladder roof and derteased in the remaining part of the bladder in electrical stimulation group. NGF was primarily located in the bladder epithelial cell membranes and the cytoplasm of detrusor cells, increased in the injured group and decreased in electrical stimulation group.Conclusion and Innovation point:1. Long-term sacral anterior root stimulation of anode block can reduce the residual urine volume, increase voiding efficiency and bladder volume, lower resting bladder pressure and detrusor leak point pressure as well as maximum detrusor pressure, recover bladder compliance, correct detrusor hyperactivity and sphincter pathology, protect the upper urinary tract, avoid effectively complications such as vesicoureteral reflux, and can reconstruct bladder voiding function after spinal cord injury, prolong survival time of rabbits with paraplegia and improve the quality of life.2. Long-term anode block sacral nerve stimulation in rabbits anterior root can protect the bladder ultrastructure, recover neurotransmitter receptors and nerve growth factor on the bladder. Through the restoration of neurotransmitter receptors and nerve growth factor to stable environment within the bladder.