Objective To investigate the effects of epidural spinal cord electrical stimulation (ESCES) on spinal cord reflexes in normal adult rats, and to find out where and how the spinal cord reflexes are generated. Methods Ten adult female Sprague Dawley rats were anaesthetized and an electrode was placed at the S, spinal cord segment. Single electric pulses with 200 μs pulse width and voltages of 400 mV, 600 mV and 1200 mV were used in the ESCES. 1200 mV voltages with 50 Hz, 60 Hz, 80 Hz, 100 Hz frequency were also tested. EMG signals were re-corded with concentric needle electrodes in the rats' semitendinosus muscles to observe the characteristics of spinal cord reflexes. Results The voltage threshold for generating semitendinosus muscle response was 300 mV. The three ESCES voltages induced 2 kinds of spinal cord reflexes. The 400 mV and 600 mV stimulation induced spinal cord reflexes with short latency (5.27±0.36 ms and 5.19±0.67 ms respectively). The 1200 mV stimulation volt-age induced spinal cord reflexes with long latency (2.57±0.23 ms). Spinal cord reflexes could be generated by 50 Hz, 60 Hz, 80 Hz, and 100 Hz ESCES. At the higher frequencies, spinal cord reflexes declined late in the ex-periments and then appeared irregular. In some of the rats, spinal cord reflexes vanished entirely late in the stimula-tion experiments. The latency and duration of the spinal cord reflexes induced by 50 Hz ESCES were (4.46 ± 1.07) ms and (7.33±1.00)ms respectively. These were significantly different from the latency and duration initia-ted by 60 Hz, 80 Hz or 100 Hz ESCES. Conclusions Different ESCES voltages induce different spinal cord refle-xes generated differently. The long latency reflexes might be monosynaptic responses mediated by dorsal root excite-ment, while the short latency reflexes might be sarcous exciting electric activity mediated by direct excitement of mo-tor neurons or motor fibers. The irregular spinal cord reflexes induced by higher frequency ESCES might be one kind of monosynaptic response. Irregularly appearing spinal cord reflexes induced by higher frequency stimulation might due to the inhibitory effect of higher frequency stimulation.

Objective:To investigate the effects of epidural spinal cord stimulation (ESCS) and treadmill training on the locomotion function and ultrastructure of spinal cord anterior horn after moderate spinal cord injury in rats. (IT, n=3). All rats received a moderate spinal cord injury surgery. Four weeks after surgery, rats in SE group received an electrode implantation procedure, with the electrode field covering spinal cord segments L2-S1. Four weeks after electrode implantation, rats received subthreshold ESCS for 30 min/d. Rats in TY group received 4cm/s treadmill training for 30min/d. Rats in SI group received no intervention, as a control group. All procedures in these three groups lasted four weeks.The open field Basso,Beattie and Bresnahan (BBB) scale was used before and after intervention to evaluate rats' hindlimb motor function. Result:After four weeks intervention, rats in TT group improved their open field locomotion scores to 20. In contrast, no significant improvement was observed in groups SI and SE. The morphology of synapses and neurons were similar regardless of whether rats had undergone ESCS, treadmill training or not. Conclusion:ESCS alone was not sufficient to improve the walking ability of spinal cord injured rats. ESCS or treadmill training alone might not contribute to the changes of ultrastructure in anterior horn of spinal cord that underlie the recovery of walking ability. Further research is needed to understand the contributions of combination of ESCS and treadmill training to the rehabilitation of spinal cord injured rats.