Effect of the artificial somato-autonomic neuroanastomosis on defecation after spinal cord injury and its underlying mechanisms

Abstract

A new artificial somatic-autonomic neuroanastomosis has been established in male rats with spinal cord injury (SCI). Anorectal manometry and neural retrograde tracing were conducted in this animal model to analyze the mechanisms and the effects on recovery of anorectal function. The left L4 ventral root (L4VR) was intradurally micro-anastomosed to the L6 ventral root (L6VR) to establish the new regenerated neural pathway. Three months later the spinal cord was completely transected at the T9-10 level. Eight weeks later the model rats were randomly divided into two groups. The rats in the group 1 (n=8) were applied for anorectal manometry, and those in the group 2 (n=4) were used for neural retrograde tracing study with fluorogold (FG) and dextran tetramethylrhodamine (TMR). The results of anorectal manometry showed the new reflex pathway could induce rectum to contract and simultaneously electric activity of external anal sphincter (EAS) to become weak or disappearing (indicating synergetic relaxation of EAS). FG and TMR dual labeled neurons with round and elliptical shape were mainly observed in L4 angulus anterior of model rats. The regenerated neural pathways were effective to improve the rectum external sphincter synergetic status and restore the anorectal function.