Myofascial pain syndrome is one of the most common forms of muscle pain. In this syndrome, pain is originated by the so-called trigger points, which consists of a set of palpable contraction knots in the muscle. It has been proposed that a high, spontaneous neurotransmission may be involved in the generation of these contraction knots. To confirm this hypothesis, we exposed mouse muscles to an anticholinesterasic agent to increase the neurotransmision in the synaptic cleft in two different conditions, in vivo and ex vivo experiments. Using intracellular recordings, a sharp increase in the spontaneous neurotransmission in the levator auris longus muscle and a lower increase in the diaphragm muscle could be seen. Likewise, electromyography recordings reveal an elevated endplate noise in gastrocnemius muscle of treated animals. These changes are associated with structural changes such as abundant neuromuscular contracted zones observed by rhodaminated α-bungarotoxin and the presence of abundant glycosaminoglycans around the contraction knots, as shown by Alcian PAS staining. In a second set of experiments, we aimed at demonstrating that the increases in the neurotransmission reproduced most of the clinical signs associated to a trigger point. We exposed rats to the anticholinesterase agent neostigmine, and 30 min afterward we observed the presence of palpable taut bands, the echocardiographic presence of contraction knots, and local twitch responses upon needle stimulation. In summary, we demonstrated that increased neurotransmission induced trigger points in both rats and mice, as evidenced by glycosaminoglycans around the contraction zones as a novel hallmark of this pathology. NEW & NOTEWORTHY In rodents, when neostigmine was injected subcutaneously, the neuromuscular neurotransmission increased, and several changes can be observed: an elevated endplate noise compared with normal endplate noise, as evidenced by electromyographyc recording; many muscular fibers with contraction knots (narrower sarcomeres and locally thickened muscle fiber) surrounded by infiltration of connective tissue like glycosaminoglycans molecules; and palpable taut bands and local twitch responses upon needle stimulation. Several of these signs are also observed in humans with muscle pain.

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Objective. Some dry needling treatments involve repetitive and rapid needle insertions into myofascial trigger points. This type of treatment causes muscle injury and can also damage nerve fibers. The aim of this study is to determine the injury caused by 15 repetitive punctures in the muscle and the intramuscular nerves in healthy mouse muscle and its ulterior regeneration. Methods. We repeatedly needled the levator auris longus muscle of mice, and then the muscles were processed with immunohistochemistry, methylene blue, and electron microscopy techniques. Results. Three hours after the dry needling procedure, the muscle fibers showed some signs of an inflammatory response, which progressed to greater intensity 24 hours after the procedure. Some inflammatory cells could still be seen when the muscle regeneration was almost complete seven days after the treatment. One day after the treatment, some changes in the distribution of receptors could be observed in the denervated postsynaptic component. Reinnervation was complete by the third day after the dry needling procedure. We also saw very fine axonal branches reinnervating all the postsynaptic components and some residual sprouts the same day. Conclusion. Repeated dry needling punctures in muscle do not perturb the different stages of muscle regeneration and reinnervation.

Objective. Multidisciplinary treatments of fibromyalgia (FM) have demonstrated efficacy. Nevertheless, they have been criticized for not maintaining their benefits and for not being studied for specific populations. Our objectives were to determine the efficacy of a multidisciplinary treatment for FM adapted for patients with low educational levels and to determine the maintenance of its therapeutic benefits during a long-term followup period. Methods. Inclusion criteria consisted of female sex, a diagnosis of FM (using American College of Rheumatology criteria), age between 18 and 60 years, and between 3 and 8 years of schooling. Patients were randomly assigned to 1 of the 2 treatment conditions: conventional pharmacologic treatment or multidisciplinary treatment. Outcome measures were functionality, sleep disturbances, pain intensity, catastrophizing, and psychological distress. Analysis was by intent-totreat and missing data were replaced following the baseline observation carried forward method. Results. One hundred fifty-five participants were recruited. No statistically significant differences regarding pretreatment measures were found between the 2 experimental groups. Overall statistics comparison showed a significant difference between the 2 groups in all of the variables studied (P < 0.0001). Mixed linear model analysis demonstrated the superiority of the multidisciplinary treatment in all of the studied variables at posttreatment. The differences were maintained at 12-month followup in sleep disturbances (P < 0.0001), catastrophizing (P < 0.0001), and psychological distress (P < 0.01). Conclusion. Multidisciplinary treatment adapted for individuals with low educational levels is effective in reducing key symptoms of FM. Some improvements were maintained 1 year after completing the multidisciplinary treatment.