Anti-hyperalgesic effect of electroacupuncture in a model of post-incisional pain in rats

Analgesic efficacy of laser acupuncture and electroacupuncture in cats undergoing ovariohysterectomy

The aim of this study was to compare the effects of laser acupuncture and electroacupuncture on postoperative pain and analgesic requirements in cats. In a prospective, randomized and blinded clinical study, thirty cats undergoing ovariohysterectomy were sedated with intramuscular (IM) ketamine (5 mg/kg), midazolam (0.5 mg/kg), and tramadol (2 mg/ kg). Before the induction of anesthesia, the animals were randomly distributed into three groups of ten cats each: LA: bilateral Stomach 36 (ST-36) and Spleen 6 (SP-6) acupoints were stimulated with an infrared laser; EA: bilateral ST-36 and SP-6 acupoints were stimulated with an electrical stimulus; Control: no acupuncture was applied. Postoperative analgesia was evaluated in the first 24 hr post-extubation using the Interactive Visual Analogue Scale and UNESP-Botucatu Multidimensional Composite Pain Scale. Rescue analgesia was provided with IM tramadol (2 mg/kg), and the pain scores were reassessed 30 min after the rescue intervention. If the analgesia remained insufficient, meloxicam (0.2 mg/kg IM, single dose) was administered. Data were analyzed using t-tests, the Mann-Whitney U test, and Friedman test. P<0.05 was considered significant. The pain scores did not significantly differ between the treatment groups at any time point (P>0.05). The prevalence of rescue analgesia was significantly higher in the Control group than in the LA and EA groups (P=0.033). Preoperative laser and electroacupuncture reduced the need for rescue analgesia during the first 24 hr after ovariohysterectomy.

Spinal p38 activity and analgesic effect after low- and high-intensity electroacupuncture stimulation in a plantar incision rat model

AIMS

Postoperative pain is a major problem. Electroacupuncture (EA) has been accepted as a useful and low-risk complementary therapy for post-operative pain. Animal studies indicate that surgical incision activates p38 MAPK in the spinal microglia, which critically contributes to post-incisional nociceptive development. How EA affects incision-induced p38 activation is important but yet to be fully elucidated.

METHODS

Male adult rats received plantar incision (PI) at the right hind paw followed by 30-min EA of 4-Hz, one of two intensities (3 and 10mA), and at right ST36 (Zusanli) acupoint immediately after PI and for 3 successive days. EA analgesia was evaluated by von Frey fibers and Hargreaves' tests. Spinal p38 activation was examined by immunostaining. In separate groups, SB203580, a p38 inhibitor, was intrathecally injected alone or with EA to test the combining effect on nociception and spinal phospho-p38.

KEY FINDINGS

EA of 10-mA significantly ameliorated mechanical allodynia, but 3-mA did not. None of them altered thermal hyperalgesia. Repeated EA could not inhibit phospho-p38 in the PI rats, contrarily, EA per se significantly induced phospho-p38 in the normal rats. Intrathecal SB203580 injection dose-dependently prevented PI-induced allodynia. Combination of low-dose SB203580 and 3-mA EA, which were ineffective individually, profoundly reduce post-PI allodynia.

SIGNIFICANCE

We demonstrated that 10-mA EA exerts a significant inhibition against post-PI mechanical hypersensitivity via a p38-independent pathway. Importantly, co-treatment with low-dose p38 inhibitor and 3-mA EA can counteract spinal phospho-p38 to exert strong analgesic effect. Our finding suggests a novel strategy to improve EA analgesic quality.

Comparison of electroacupuncture and morphine-mediated analgesic patterns in a plantar incision-induced pain model

Electroacupuncture (EA) is a complementary therapy to improve morphine analgesia for postoperative pain, but underlying mechanism is not well-known. Herein, we investigated EA-induced analgesic effect in a plantar incision (PI) model in male Sprague-Dawley rats. PI was performed at the left hind paw. EA of 4 Hz and high intensity or sham needling was conducted at right ST36 prior to PI and repeated for another 2 days. Behavioral responses to mechanical and thermal stimuli, spinal phospho-ERK, and Fos expression were all analyzed. In additional groups, naloxone and morphine were administered to elucidate involvement of opioid receptors and for comparison with EA. EA pretreatment significantly reduced post-PI tactile allodynia for over 1 day; repeated treatments maintained analgesic effect. Intraperitoneal naloxone could reverse EA analgesia. Low-dose subcutaneous morphine (1 mg/kg) had stronger inhibitory effect on PI-induced allodynia than EA for 1 h. However, analgesic tolerance appeared after repeated morphine injections. Both EA and morphine could equally inhibit PI-induced p-ERK and Fos inductions. We conclude that though EA and morphine attenuate postincision pain through opioid receptor activations, daily EA treatments result in analgesic accumulation whereas daily morphine injections develop analgesic tolerance. Discrepant pathways and mechanisms underlying two analgesic means may account for the results.

Effect of Electroacupuncture Intervention on Expression of CGRP, SP, COX-1, and PGE2 of Dorsal Portion of the Cervical Spinal Cord in Rats with Neck-Incision Pain

The present study was aimed to determine if cervicospinal substance P (SP) and its neurokinin-1 receptor (NK-1R), calcitonin gene-related peptide (CGRP), cyclooxygenase-1 (COX-1), and prostaglandin E2 (PGE2) were involved in electroacupuncture (EA) analgesia in neck-incision pain rats. EA intervention was applied to bilateral Futu (LI18), Hegu (LI4)-Neiguan (PC6), and Zusanli (ST36)-Yanglingquan (GB34) for 30 min. Cervicospinal SP and CGRP immunoactivity was detected by immunofluorescence technique, NK-1R and COX-1 protein and mRNA expression levels were determined using Western blot and real-time PCR, respectively, and PGE2 content was measured using ELISA. Outcomes indicated that EA of EA-LI18 and LI4-PC6 (not ST36-GB34) significantly suppressed neck-incision induced decrease of thermal pain threshold (P < 0.05). EA stimulation of LI18 and LI4-PC6 markedly inhibited neck-incision induced upregulation of SP and CGRP immunoactivity, NK-1 R and COX-1 mRNA and protein expression levels, as well as the increase of PGE2 content in the dorsal cervicospinal cord (P < 0.05). These findings showed that LI18 and LI4-PC6 EA stimulation-induced downregulation of SP, CGRP, NK-1R, COX-1, and PGE2 levels in the dorsal cervicospinal cord may contribute to their effects in relieving neck-incision pain. This study highlights the targets of EA intervention for reducing post-thyroid-surgery pain for the first time.

Electroanalgesia for the postoperative control pain in dogs

PURPOSE

To evaluate the analgesic and neuroendocrine effects of electroanalgesia in dogs undergoing ovariohysterectomy.

METHODS

Eighteen dogs were randomly distributed to three groups of six animals each and received either electrical stimuli at acupuncture points (EA), at peri-incisional dermatomes (DER) and at both acupuncture points and peri-incisional dermatomes (EAD). Pre-anesthetic medication was acepromazine (0.05mg kg-1, IV). Anesthesia was induced with propofol (4 to 5mg kg-1, IV) and maintained with isoflurane. Postoperatively pain degree was measured using a numerical rating scale. Dogs were scored at 1, 3, 6, 12 and 24 hours postoperative. If the pain score was ≥6, supplemental morphine (0.5mg kg-1, IM) was administered. Serum cortisol concentration was measured before pre-anesthetic medication (basal), and at 1, 12 and 24 hours postoperative.

RESULTS

EA and EAD- treated dogs had lower pain scores than DER treated dogs one hour postoperatively. Fewer EA and EAD-treated dogs required rescue analgesia. Serum cortisol did not differ among treatments.

CONCLUSION

Preoperative application of electrical stimuli to acupuncture points isolated or in combination with peri-incisional dermatomes provides a reduced postoperative opioid requirement and promotes an effective analgesia in dogs undergoing ovariohysterectomy.

High-frequency electroacupuncture versus carprofen in an incisional pain model in rats

The objective of the present study was to compare the effect of electroacupuncture (EA) and carprofen (CP) on postoperative incisional pain using the plantar incision (PI) model in rats. A 1-cm longitudinal incision was made through skin, fascia and muscles of a hind paw of male Wistar rats and the development of mechanical and thermal hypersensitivity was determined over 4 days using the von Frey and Hargreaves methods, respectively. Based on the experimental treatments received on the third postoperative day, the animals were divided into the following groups: PI+CP (CP, 2 mg/kg, po); PI+EAST36 (100-Hz EA applied bilaterally at the Zusanli point (ST36)); PI+EANP (EA applied to a non-acupoint region); PI+IMMO (immobilization only); PI (vehicle). In the von Frey test, the PI+EAST36 group had higher withdrawal force thresholds in response to mechanical stimuli than the PI, PI+IMMO and PI+EANP groups at several times studied. Furthermore, the PI+EAST36 group showed paw withdrawal thresholds in response to mechanical stimuli that were similar to those of the PI+CP group. In the Hargreaves test, all groups had latencies higher than those observed with PI. The PI+EAST36 group was similar to the PI+IMMO, PI+EANP and PI+CP groups. We conclude that 100-Hz EA at the ST36 point, but not at non-acupoints, can reduce mechanical nociception in the rat model of incisional pain, and its effectiveness is comparable to that of carprofen.

Acupuncture Stimulation at Sanyinjiao: Effect on the Sodium Pertechnetate Bioavailability in Rats

In clinical acupuncture, when acupuncture points are stimulated, several types of reflex responses can be evoked. Consequently, different categories of physiological responses are induced, which include changes in the activities of internal organs and tissues. The acupuncture point Sanyinjiao (SP6) has been used successfully to treat different human gastrointestinal conditions. The aim of this work was to investigate the effects of end-organ response induced by acupuncture point SP6 on the bioavailability of the radiopharmaceutical sodium pertechnetate ( Na 99 m TcO 4) in Wistar rats. Healthy rats were allocated into 2 groups, control-CG and treated-TG. TG was bilaterally stimulated at acupuncture point SP6 with stainless steel needles. Ocular plexus administration of Na 99 m TcO 4 (3.7MBq) was carried out 10 min after every needle insertion in all animals. Ten minutes later, the animals were killed, the organs were isolated, the radioactivity was determined in a well gamma counter, and the percentage of injected dose per gram of tissue (%ID/g) was determined for each organ. The %ID/g was significantly altered ( p < 0.05) in the small intestine of TG (0.56 ± 0.09) when compared to CG (0.82 ± 0.18). These results may suggest that this stimulation might induce physiological responses capable of altering the bioavailability of the radiopharmaceutical sodium pertechnetate. These findings aid in providing a better understanding of acupuncture and its effects on various organs and tissues.

Electroacupuncture analgesia in dogs: is there a difference between uni- and bi-lateral stimulation?

OBJECTIVE

To compare the analgesic effect of uni- and bi-lateral electroacupuncture (EA) in response to thermal and mechanical nociceptive stimuli and to investigate the cardiorespiratory, endocrine, and behavioral changes in dogs submitted to EA.

STUDY DESIGN

Prospective, randomized cross-over experimental study.

ANIMALS

Eight adult, clinically healthy, cross-breed dogs, weighing 13 +/- 4 kg.

METHODS

Dogs underwent electrostimulation at false acupoints (T-false); bilateral EA at acupoints, stomach 36, gall bladder 34 and spleen 6 (T-EA/bil); unilateral EA at the same points (T-EA/uni) or were untreated (T-control). All animals received acepromazine (0.05 mg kg(-1)) IV; and heart rate, pulse oximetry, indirect arterial blood pressure, respiratory rate, Pe'CO(2), rectal temperature, and plasma cortisol concentration were measured before, during, and after EA. Analgesia was tested using thoracic and abdominal cutaneous thermal and mechanical stimuli, and an interdigital thermal stimulus. Behavior was classified as calm or restless. Analysis of variance for repeated measures followed by Tukey's test was used for analysis of the data.

RESULTS

There were no cardiorespiratory differences among the treatments. The cutaneous pain threshold was higher after EA, compared with false points. The latency period was shorter and analgesia was more intense in T-EA/bil than T-EA/uni, when both were compared with T-false and T-control. Six out of eight animals treated with EA were calm during treatment, and 5/8 and 4/8 of the T-false and T-control animals, respectively, were restless. Latency to interdigital thermal stimulation increased in T-EA/bil compared with the others. There was no difference in plasma cortisol concentrations among the treatments.

CONCLUSIONS

Bilateral EA produced a shorter latency period, a greater intensity, and longer duration of analgesia than unilateral stimulation, without stimulating a stress response.

CLINICAL RELEVANCE

Bilateral EA produces a better analgesic effect than unilateral EA.