Somatosensory evoked potentials (SSEPs) are a sensitive quantitative measure of conduction in somatosensory pathways of the central nervous system and are increasingly used in both clinical trials and animal experiments. SSEPs can be recorded in non-sedated rodents by magnetic stimulation (MS) of peripheral nerves. To overcome some disadvantages caused by using anesthesia and implanted recording electrodes, we used subdermal needle electrodes located on the midline of the skull to successfully record SSEPs in non-sedated rats, elicited by stimulating the tibial nerve with a magnetic stimulator. The wave form contains a typical P1 peak and N1 peak. Although there is a variation of P1 latency, N1 latency, and P1-N1 amplitude between right side and left side, it was not statistically significant. In addition, there is a significantly positive relationship between P1-N1 amplitude and MS strength, suggesting that the increase in magnetic stimulating strength resulted in the increase in P1-N1 amplitude. Results in the present study demonstrate that our modified method is a reliable and feasible paradigm for recording SSEPs in non-sedated rats.
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