The new method of placebo IFC was effective for blinding of research investigators and most of the active IFC-treated subjects, promoting an appropriate placebo method.

Background. Injections of acidic saline into the gastrocnemius muscle in rats produce a bilateral long-lasting hyperalgesia similar to fibromyalgia in humans. No previous study investigated the effect of electroacupuncture (EA) on this acidic saline model. This study aimed to identify the effects of EA in the hyperalgesia produced by repeated intramuscular injections of acidic saline. Methods. Rats were divided into four groups (n = 6, each group): control, acupuncture, EA 15 Hz, and 100 Hz. Left gastrocnemius muscle was injected with 100 μL of pH 4.0 sterile saline twice five days apart. EA, acupuncture, or control therapy was daily administered (20 min) for 5 consecutive days under anesthesia. Needles were placed in the St36 and Sp6 acupoints. The assessment of secondary mechanical hyperalgesia, thermal hyperalgesia, and motor performance was performed before injections and before and after the treatment performed on each day. The paw withdrawal threshold was tested using the nonparametric Kruskal-Wallis test and differences within the group Wilcoxon Matched Pairs. The latency and motor performance were tested for ANOVA parametric test for independent measures, and for differences in the group, we used t-test for paired samples. Post hoc Tukey test was used for multiple corrections. P values less than 0.05 were considered statistically significant. Results. Indicate that there was a significant reduction of mechanical withdrawal threshold and paw withdrawal latency 24 hours following the second injection. Moreover, mechanical and thermal hyperalgesia were significantly reversed by EA 15, 100 Hz, and acupuncture. Conclusions. The results suggest that EA high and low frequency as well as acupuncture are effective in reducing hyperalgesia in chronic muscle pain model.

This study aimed to identify the effects of electroacupuncture in the mechanical hyperalgesia produced by repeated intramuscular injections of acidic saline. Twenty four male Wistar rats were divided in four groups (n = 6, in each group): control, acupuncture, electroacupuncture (EA) 15 Hz and electroacupuncture (EA) 100 Hz. Left gastrocnemius muscle from all animals was injected with 100 μL of sterile saline pH 4.0 twice five days apart. Electroacupuncture, acupuncture or control was daily administered (20 min) for 5 consecutive days under isoflurane anesthesia (1%–2%). Needles were placed in the Zuzanli (St36) and Sanyinjiao (SP6). Paw withdrawal threshold to mechanical stimuli was assessed before the two injections, and before and after the each stimulation by using von Frey filaments. The reduced paw withdrawal threshold that occurs 24 hours after the second injection was significantly reversed by the first administration of EA at both 100 Hz and 15 Hz when compared with sham treatment and baseline measures. The analgesic effect lasted for 4 and 3 days when 15 Hz and 100 Hz were applied, respectively. These data suggest that both 15 Hz and 100 Hz electroacupuncture are effective on reducing secondary mechanical hyperalgesia showing a long‐lasting effect. Research support: CAPES, Fapitec.