Effect of Varying Frequency and Duration of Electroacupuncture Stimulation on Carrageenan-Induced Hyperalgesia

Abstract

Objective Although electroacupuncture (EA) therapy is used to relieve various kinds of pain, the optimal frequency and duration of EA remain unclear. We investigated the effect of varying frequency and duration of EA during hyperalgesia elicited by carrageenan-induced inflammation. Methods Carrageenan was administered by subcutaneous intraplantar injection to induce inflammation. Nociceptive thresholds were measured using the paw pressure threshold (PPT) (Randall-Selitto Test). EA was applied at 3, 15, or 100Hz to the left anterior tibial muscles for 1, 15, or 60 minutes. Intensities used were chosen within the known tolerance of the animal, and increased up to 3mA for 3Hz, and up to 1.5mAfor 15 and 100Hz. EA was started three hours after carrageenan injection. Results Three hours after carrageenan injection, a marked ipsilateral inflammatory response appeared and PPT decreased significantly. This decrease persisted for at least 24 hours after carrageenan injection. EA at 3Hz (60 minutes) resulted in significant increases of PPT which persisted for 24 hours after injection. EA at 3Hz (15 minutes) also induced PPT elevations immediately and for one hour after EA compared to the control group. However, no other variety of EA significantly increased PPT. Conclusion These results show that EA produces electroacupuncture analgesia of carrageenan-induced hyperalgesia. These findings also suggest that, among the frequencies and durations tested, EA at 3Hz (60 minutes) is the most suitable frequency and duration for carrageenan-induced inflammation. It seems that EA has different analgesic effects and mechanisms according to the parameters of stimulation. For EA in the clinical induction of analgesia, it is especially important that an effective frequency and duration are selected.

Electroacupuncture analgesia with different frequencies is mediated via different opioid pathways in acute visceral hyperalgesia rats

“…The analgesic durations of the three different frequencies were significantly longer than that of previous studies with uninjured animal models, which showed only a short duration (20-60 min) of acupuncture analgesia [34][35][36]. However, several other reports have showed that acupuncture produces long-term therapeutic pain relief lasting for hours or even days in animals with inflammatory conditions [27,28,33,38]. One possible explanation is that the EA treatments were applied under mild anesthesia with uninjured animal models.…”

Randomised Controlled Trial of Contralateral Manual Acupuncture for the Relief of Chronic Shoulder Pain

“…Several randomised controlled trials (RCTs) have investigated the effects of acupuncture for the treatment of shoulder pain, with different combinations of acupuncture points, treatment protocols and methods of needle stimulation, [4][5][6][7][8][9][10][11][12][13][14] all of which potentially influence the therapeutic outcome of acupuncture treatment. [15][16][17][18][19] While most acupuncture trials have involved acupuncture needling close to the site of pathology, with or without addition of distal or contralateral acupuncture points, many Chinese medical practitioners purely use acupuncture points contralateral to the site of pain to treat unilateral limb pain, such as that arising from the shoulder or leg. 15 20 However, there is little scientific evidence to validate the clinical effects of contralateral acupuncture in morbid subjects, despite there having been several studies in animals and healthy human volunteers.…”

Comparison of Electroacupuncture in Restrained and Unrestrained Rat Models

“…It is generally accepted that EA promotes the release of analgesic substances such as opioids [4]. However, more recent work indicated distinct mechanisms of EA analgesia between different stimulating frequencies [4, 7], durations [7, 8], intensities [5, 6, 9], locations [2], and subject conditions (healthy versus pathological states) [13]. Thus, various experimental designs and techniques should be applied in combination towards a comprehensive elucidation of EA mechanisms.…”