Increased evoked EMG thresholds for tail muscles in a rat cauda equina (CE) injury model

Abstract

CE injuries comprise ~15% of new spinal injuries every year in the US. Despite this high incidence, CE trauma is rarely studied. Therefore, we are currently developing a rat hemi-CE model for the purpose of investigating therapies that may promote functional recovery. A laminectomy was performed at L6 on adult female Sprague Dawley rats followed by opening of the dura and crushing of the right side nerve roots (i.e. the hemi-cauda). One week post-injury the right hemi-cauda at L6 was again isolated and placed onto a stimulating electrode with the crushed region caudal to the electrode. Recording needle electrodes were located at the proximal (P), middle (M), and tip (T) of the right tail to measure the voltage required (1 ms pulse duration) to elicit an EMG response. Thresholds (V) were higher in injured rats compared to those with only a laminectomy (control (n=3) vs. injured (n=5); MEAN ± SEM): P (2.2 ± 0.03 vs. 3.3 ± 0.48), M (2.3 ± 0.13 vs. 3.0 vs. 0.36), and T (2.3 ± 0.12 vs. 5.5 ± 0.97). No response was observed in 2 of the 5 CE rats at site T. We are currently initiating additional measures to quantify tail function in both conscious and anesthetized rats to further verify the loss of motor output. Our results suggest that a rat model of hemi-CE injury can be utilized to investigate interventions that may promote nerve root regeneration and concomitant improvement of motor function. # 40424: Central NY Biotechnology Research Center; NASA