100-Hz Electroacupuncture but not 2-Hz Electroacupuncture is Preemptive Against Postincision Pain in Rats

Abstract

Preemptive analgesia involves introducing an analgesic before noxious stimulation. Electroacupuncture (EA) activates descending mechanisms that modulate nociceptive inputs into the spinal dorsal horn. This study evaluated whether preoperative EA is more effective than postoperative EA in reducing incision pain in rats. The nociceptive threshold to mechanical stimulation was utilized to examine the effects of an intraperitoneal injection of saline (0.1 mL/kg) or naloxone (1 mg/kg) on antinociception induced by a 20-minute period of 2-Hz or 100-Hz EA applied to the Zusanli (ST36) and Sanyinjiao (SP6) acupoints before surgical incision, or 10 minutes after or 100 minutes after surgical incision of the hind paw. The extent of mechanical hyperalgesia after the incision was significantly attenuated by the application of 100-Hz EA preoperatively, but not by its application at 10 minutes or 100 minutes postoperatively. By contrast, 2-Hz EA was effective against postoperative hyperalgesia when applied 10 minutes or 100 minutes after surgery but not when it was applied preoperatively. Only the effect of 2-Hz EA applied 10 minutes after surgery was sensitive to naloxone. The present study showed for the first time that 100-Hz EA, but not 2-Hz EA, exerts a nonopioidergic preemptive effect against postincision pain in rats.

Electroacupuncture Stimulation Alleviates CFA-Induced Inflammatory Pain Via Suppressing P2X3 Expression

“…However, we have demonstrated that the analgesic effect of EA was greater at 100 Hz than at 2 Hz in the scenario of inflammatory pain [7]. Similarly, 100 Hz, but not 2 Hz EA stimulation, could relieve post-incision pain [23]. In addition to the frequency, the number of stimulations may also significantly affect the analgesic effects of EA, indicative of the presence of a cumulative effect [24,25].…”

The preemptive analgesia of pre-electroacupuncture in rats with formalin-induced acute inflammatory pain

“…Consistent with our results, recent studies had demonstrated the expected outcome of EA and its preemptive analgesia. 14,16 However, one of the previous study insisted that 100-Hz EA, instead of 2-Hz EA, was preemptive against incision pain in rats, whereas 2-Hz EA was more effective for postincision analgesia. 16 A possible explanation for this contradiction might be the difference of EA acupoints and stimulating spontaneous time between two studies.…”

“…14,16 However, one of the previous study insisted that 100-Hz EA, instead of 2-Hz EA, was preemptive against incision pain in rats, whereas 2-Hz EA was more effective for postincision analgesia. 16 A possible explanation for this contradiction might be the difference of EA acupoints and stimulating spontaneous time between two studies. Accordingly, ipsilateral Zusanli (ST36) and Weizhong (BL40) were stimulated for 30 min with 2-Hz/1 mA EA in our experiment, and based on the "JingMai" theory of traditional Chinese medicine, ST36 and BL40 are the most valuable acupoints for treating the lower limbs pain.…”

“…[10][11][12][13] Interestingly, there is an evidence that pre-EA exerts a satisfactory analgesic effect against postincision pain in rats. [14][15][16] Although there was a lack of clarification, these results showed us a novel strategy for nonpharmacological preemptive analgesic option. Thus, one purpose of our study is to confirm the preemptive analgesic effect of EA.…”