Cortical motor evoked potentials

Four weeks after graft implantation, canines (n = 4 in the NF‐GS group and n = 4 in the F‐GS group) were atropinized (0.5 mg/canine, intramuscular injection, 20 min before surgery), anesthetized with pentobarbital sodium (3% dissolved in saline, 45 mg/kg, intraperitoneal injection) and ketamine (10 mg/kg, intramuscular injection every 20 min during surgery), and fixed on a stereotaxic frame. The sciatic nerve and sensorimotor cortex (SMC) were exposed; a stimulation electrode was then connected to the SMC and a recording electrode was coupled to the sciatic nerve [Fig. ​[Fig.4(B)].4(B)]. The cortical motor evoked potentials (CMEP) were detected by NeuroExam M‐800 (Medcom Technology, Zhuhai, China). The stimulation protocol of the CMEP signal was as follows: gain parameter 250, time constant 150 μs, and pulse width 100 mA. To elicit a CMEP, multiple‐pulse‐stimulation was transmitted through the electrodes, with an interval of 1000 μs for 4 times. In order to obtain high‐quality waveforms for the CMEP signals, 40 CMEP responses were averaged for each canine.

Examination of cortical motor evoked potentials (CMEP). A: CMEPs in the NF‐GS (upper curves) and F‐GS (lower curves) groups were respectively recorded by electrophysiological analysis before spinal cord injury, at 1 week and 4 weeks after the transplantation. B: A leading diagram showing evaluation of CMEP. Left panel: stimulus points in head; Right panel: recorder points in the leg of the hemisection site. C: Bar chart showing latency of CMEPs of two groups of canines at 4 weeks after scaffold transplantation (n = 4, *p < 0.05). D: Bar chart showing amplitude of two groups at 4 weeks after transplantation (n = 4, *p < 0.05).