Modulatory effect of respiration triggered trans-spinal magnetic stimulation on diaphragmatic motor evoked potentials following cervical spinal cord contusion in rats

The present study aimed to establish a respiration-triggered trans-spinal magnetic stimulation protocol and to examine its modulatory effects on bilateral diaphragmatic motor evoked potentials in the context of cervical spinal cord injury. The assessment of diaphragmatic motor evoked potentials induced by trans-spinal magnetic stimulation was conducted during both inspiratory and expiratory phases in spinal-intact and cervical spinal cord contused rats. The findings showed that inspiration-triggered trans-spinal magnetic stimulation produced a significantly greater bilateral diaphragmatic motor evoked potential response compared to the response induced by expiration-triggered stimulation in uninjured animals. In addition, high-intensity inspiration-triggered trans-spinal magnetic stimulation was found to reduce diaphragmatic bursting that occurred subsequent to the motor evoked potential (i.e., post-motor evoked potential activity). In cases of cervical spinal cord contusion, there was a notable reduction in inspiratory diaphragmatic activity, which also affected the diaphragmatic motor evoked potentials induced by trans-spinal magnetic stimulation. Specifically, the respiratory modulatory effects of trans-spinal magnetic stimulation on diaphragmatic motor evoked potentials were diminished in the diaphragm ipsilateral to the injury. Furthermore, the inhibitory effects of inspiration-triggered trans-spinal magnetic stimulation on post-motor evoked potential activity were also less pronounced in the contused animals. These results suggest that the influence of trans-spinal magnetic stimulation on diaphragmatic motor evoked potentials is modulated by the respiratory phase, indicating that respiration-triggered trans-spinal magnetic stimulation may serve as a valuable tool for assessing alterations in diaphragm excitability and spinal respiratory circuitry following cervical spinal cord injury. National Science and Technology Council (112-2636-B-110-001 & 112-2628-B-110-003-MY3) This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.