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Evidence-Based Complementary and Alternative Medicine
Volume 2015, Article ID 404971, 8 pages
http://dx.doi.org/10.1155/2015/404971
Research Article

Myelinated Afferents Are Involved in Pathology of the Spontaneous Electrical Activity and Mechanical Hyperalgesia of Myofascial Trigger Spots in Rats

1Department of Physical Medicine & Rehabilitation, Qilu Hospital of Shandong University, No. 107, Wenhuaxi Road, Jinan, Shandong 250012, China
2Laboratory for Musculoskeletal Pain and Motor Control, Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7, Building D3, 9220 Aalborg, Denmark

Received 13 March 2015; Accepted 16 April 2015

Academic Editor: Ke Ren

Copyright © 2015 Fei Meng et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Myofascial trigger points (MTrPs) are common causes for chronic pain. Myelinated afferents were considered to be related with muscular pain, and our clinical researches indicated they might participate in the pathology of MTrPs. Here, we applied myofascial trigger spots (MTrSs, equal to MTrPs in human) of rats to further investigate role of myelinated afferents. Modified pyridine-silver staining revealed more nerve endings at MTrSs than non-MTrSs (), and immunohistochemistry with Neurofilament 200 indicated more myelinated afferents existed in MTrSs (). Spontaneous electrical activity (SEA) recordings at MTrSs showed that specific block of myelinated afferents in sciatic nerve with tetrodotoxin (TTX) led to significantly decreased SEA (). Behavioral assessment showed that mechanical pain thresholds (MPTs) of MTrSs were lower than those of non-MTrSs (). Block of myelinated afferents by intramuscular TTX injection increased MPTs of MTrSs significantly (), while MPTs of non-MTrSs first decreased () and then increased (). 30 min after the injection, MPTs at MTrSs were significantly lower than those of non-MTrSs (). Therefore, we concluded that proliferated myelinated afferents existed at MTrSs, which were closely related to pathology of SEA and mechanical hyperalgesia of MTrSs.