This study aimed to evaluate the acute effects of TENS at acupuncture points LI4 and SJ3 on PREPs to characterize acupuncture's influence on nociception.
Thirty healthy participants were enrolled in the study. Their median nerves were electrically stimulated to elicit PREPs. Stimulus intensity was adjusted to a level that produced a 4/10 pain rating on the Visual Analog Scale (VAS) in participants, and PREP recordings were obtained at this intensity. A transcutaneous electrical nerve stimulation (TENS) device was used to stimulate the acupuncture points LI4 (Hegu) or SJ3 (Zhongzhu) with a pulse width of 50 ms and a frequency of 2 Hz for 15 minutes. Serial PREP recordings were conducted before (pre-treatment), immediately after, and five minutes post-treatment following a 15-minute TENS stimulation session at these acupuncture points to assess changes in the latency and amplitudes of PREP peak waveforms. The peak waves P8, N9, N11, N13, and N20 were collected from short-term and long-term PREPs. Their latencies and amplitudes were analyzed in this study.
For the RPEP measures, no significant differences were observed in the N9, N11, and N13 waves among the three time points for latency or amplitude (p > 0.05). For the P8 wave, no significant main effect of time (p > 0.05) was observed for either amplitude or latency. However, a significant interaction between time and acupuncture points (p 0.05) was detected for latency. Specifically, the latency of the P8 wave significantly increased at the five-minute post-treatment time point at LI4 point compared to the pre-stimulation value (p 0.05). Additionally, the latency of the N20 wave significantly increased immediately after TENS stimulation at SJ3 point compared to the pre-stimulation value (p 0.05).
Based on the findings of this study, TENS stimulation at acupuncture points LI4 and SJ3 demonstrated acute effects on PREP peak waveforms. While no significant changes were observed for N9, N11, and N13 waves, the P8 and N20 waves showed notable alterations in latency. Specifically, the latency of the P8 wave significantly increased at the five-minute post-treatment time point at LI4, suggesting a delayed response to nociceptive stimuli, especially at Erb's point. Additionally, the immediate increase in N20 wave latency after TENS stimulation at SJ3 points indicates a potential influence on thalamocortical and cortical nociceptive processing.
These findings suggest that acupuncture point stimulation through TENS may modulate nociceptive pathways in a complex manner, potentially offering therapeutic benefits for pain management. Further research is needed to elucidate the precise underlying mechanisms and explore the clinical implications of these findings.
Pain evoked potentials
Nociception
