Effect of injury on S1 dorsal root ganglia in an experimental model of neuropathic faecal incontinence

Abstract

An experimental model of neuropathic faecal incontinence has recently been established. This study aimed to quantify and compare the effect of crush and compression injury on first-order sensory neurones of the inferior rectal nerve (IRN) using a nuclear marker of axonal injury, activating transcription factor (ATF) 3. Eighteen Wistar rats were allocated to three groups: an unoperated control group, an IRN crush group (positive control) and a retrouterine balloon compression group. Five days after surgery, all animals were anaesthetized and perfused with fixative, and S1 dorsal root ganglia (DRG) were harvested. The tissue was sampled and neuronal nuclear ATF-3 expression calculated. Estimated total S1 DRG ATF-3 nuclear labelling was higher in the nerve crush (median (interquartile range) 171 (60-824) cells) and balloon compression (59 (20-274) cells) groups, compared with that in the unoperated control group (9 (3-24) cells) (P = 0.001 and P = 0.008 respectively). In all groups, most neurones displaying the marker of injury were of the C-fibre class. This study confirmed the presence of axonal injury in a pelvic compression model of obstetric injury. C-fibre afferent pathways appeared to be most vulnerable. Neuromodulation may function through augmentation of residual C-fibre pathways.