The Establishment And Morphological Investigation Of An Artificial Somatic-CNS-Autonomic Reflex Arc After SCI

Since breakthroughs are absent in the research on spinal cord regeneration to date, urination and defecation disorders caused by spinal cord injury (SCI) after severe trauma remain a tough problem facing orthopedists. Neurogenic bladder dysfunction, which leads to serious urinary retention and infections of the urinary tract, and even chronic renal failure, is the leading cause of death in paraplegic patients. In addition, ever-increasing SCI patients give rise to grave economic and societal issues. Traditional treatments targeting bladder-controlling nerve roots and detrusor muscles, such as bladder denervation, electrically or magnetically stimulated urination, and detrusor musculoplasty, bring about poor effects and have many limitations. Over recent years, researchers, basing on previous studies on bladder reinnervation, have constructed the artificial bladder reflex arcs using intact somatic reflexes under the paraplegic level, helping the patients maintain controllable urination. Hence, without being aided by instruments or equipment, SCI patients can partially or mostly recover bladder urination after surgery on the remnant spinal cord and nerves, which provides a bright future for unraveling this medical problem. The progress in the diagnosis and treatment of SCI and the increasing application and improvement of microsurgical techniques has provided favorable conditions for the treatment of post-SCI nervous bladder.Since the 1990s, by improving operative methods and techniques and by using the remnant spinal reflexes, many authors have helped SCI patients maintain controllable urination, thus achieving breakthroughs in this field. In 1998, Hou CL first reconstructed the artificial tendon-spinal cord center-bladder reflex arc using the remnant achilles reflex under the paraplegic level in 8 patients, resulting in satisfactory therapeutic effects. In 2003, Zhang SC attempted to reestablish the urination and defecation functions in 30 paraplegic patients by using selective anastomosis of intercostal nerves with blood vessels with sacral nerve roots, resulting in recovery of active urination in 23 patients. In 15 paraplegic patients with functional disorders of the detrusor muscles and sphincter of the bladder, Xiao CG retained the left dorsal root (DR) of L 5 nerve root, and anastomosed L 5 nerve root with the ventral root (VR) of S or S 3 nerve root. Of these patients treated, 10 attained satisfactory control over the bladder, and their renal function, detrusor reflex, and coordination of detrusor muscles and sphincters ameliorate or turn normal. Since then, the authors have confirmed by morphological, electrophysiological, and functional means that after anastomosis of the motor efferent limb of the somatic nerve with autonomic nerve, the former grows, through regenerated axons, into parasympathetic fibers of the latter, transmitting motor impulse soundly. Aimed at understanding the mechanism underlying the crossover somatic-CNS-autonomic reflex pathway for micturition, we studied its eferent neuron localization, neurotransmiters and the ultra-structure of the MPG.Methods:1. The somatic-CNS-autonomic reflex pathway was established in rats by intral-dural microanastomosis of the left 14 ventral root (VR) to L6 ventral root (VR), while leaving the L4 doral root( DR) intact as afferent. Retrograde tracing with DiI to investigate the artificial somatic-autonomic reflex pathway.2. After DiI was injected into the left MPG, the transmitters Ach of DiI labeled neurons in spinal cord were studied by immunohistochemical technique., the major transmitters of the left MPG was also analyzed by ChAT immunohistochenmical technique, and the axons in wall of bladder were analyzed by acetylcholinesterase (AchE) histochemical technique.3. The structure of the left MPG was investigated under LM and EM after the L4VR to L6VR anastomosis for a somatic-autonomic reflex pathway.Results:1. The bladder efferent pathways were constructed, which provided an animal model for contructing nervous pathways for autonomous urination by nervous bladder caused by SCI. After DiI was injected into the left major pelvic ganglia (MPG) , DiI labeled neurons were observed in left side locus of the midial motor nuclei and lateral motor nuclei form L3 caudal to L5 rostral.2. Specific staining was observed under fluorescence microscope. ChAT-like immunopositive substance was partly distributed coincidently with the DiI labeled neurons. Double staining revealed that about 68% (8/12) ChAT positive neurons also showed DiI positive. Most of the neurons that project to the bladder were distributed in the main body of MPG. The neurons were positive for ChAT. In the wall of bladder, the acetylcholine esterase reaction stained all the nerves and the nerve trunks symmetrically, including the small trunks close to the muscles bundles.3. The structure of the left MPG was investigated under EM can show the synapse regeneration. The clear vesicles can find near the presynaptic membrane.Conclusion:1. Somatic motor axons can regeneration into peripheral autonomic and somatic motor nerves, thus resulting in a unique somatic-autonomic reflex arc. Somatic motor axons replace autonomic nerves may be the major neural anatomy infrastructure for controllable voiding via the somatic-autonomic reflex arc.2. Ach is the main transmitter of spinal cord efferent neurons of the artificial somatic-autonomic reflex arc. The neurons reinnervating MPG were Ach positive. The transmitter of MPG neurons projecting to the bladder are also Ach. The same transmitter of preganglionic fibers and postganglionic fibers in MPG may the another reason for recovering the bladder control after established the artificial reflex arc.3. Somatic motor nerve can regeneration into and replace autonomic preganglionic axons, the ultra-structures of the MPG generally similar to those of the normal MPG.