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Updated: Apr 10, 2026
Chronic Post-Ischemia Pain Model for Complex Regional Pain Syndrome Type-I in Rats
Published on: January 21, 2020
Myelinated Afferents Are Involved in Pathology of the Spontaneous Electrical Activity and Mechanical Hyperalgesia of
Fei Meng1, Hong-You Ge2, Yong-Hui Wang1
1Department of Physical Medicine & Rehabilitation, Qilu Hospital of Shandong University, No. 107, Wenhuaxi Road, Jinan, Shandong 250012, China.
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 (P < 0.01), and immunohistochemistry with Neurofilament 200 indicated more myelinated afferents existed in MTrSs (P < 0.01). 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 (P < 0.05). Behavioral assessment showed that mechanical pain thresholds (MPTs) of MTrSs were lower than those of non-MTrSs (P < 0.01). Block of myelinated afferents by intramuscular TTX injection increased MPTs of MTrSs significantly (P < 0.01), while MPTs of non-MTrSs first decreased (P < 0.05) and then increased (P > 0.05). 30 min after the injection, MPTs at MTrSs were significantly lower than those of non-MTrSs (P < 0.01). Therefore, we concluded that proliferated myelinated afferents existed at MTrSs, which were closely related to pathology of SEA and mechanical hyperalgesia of MTrSs.
Insights
Myofascial trigger spots (MTrSs) in rats show increased myelinated afferents, contributing to spontaneous electrical activity and mechanical hyperalgesia, common in chronic pain conditions.
Area of Science:
- Neuroscience
- Pain Research
- Musculoskeletal System
Background:
- Myofascial trigger points (MTrPs) are a frequent source of chronic pain.
- Clinical studies suggest myelinated afferents may play a role in MTrP pathology.
Purpose of the Study:
- To investigate the role of myelinated afferents in myofascial trigger spots (MTrSs) using a rat model.
- To determine the relationship between myelinated afferents and the pain associated with MTrSs.
Main Methods:
- Utilized modified pyridine-silver staining and Neurofilament 200 immunohistochemistry to identify nerve endings and myelinated afferents in MTrSs.
- Recorded spontaneous electrical activity (SEA) in MTrSs and assessed mechanical pain thresholds (MPTs).
- Administered tetrodotoxin (TTX) to selectively block myelinated afferents in the sciatic nerve and via intramuscular injection.
Main Results:
- MTrSs exhibited significantly more nerve endings and myelinated afferents compared to non-MTrSs (P < 0.01).
- Blocking myelinated afferents with TTX reduced SEA in MTrSs (P < 0.05).
- MPTs were lower in MTrSs, and intramuscular TTX injection increased MPTs in MTrSs (P < 0.01), while non-MTrSs showed transient changes.
Conclusions:
- Proliferated myelinated afferents are present in MTrSs.
- These myelinated afferents are closely linked to the spontaneous electrical activity and mechanical hyperalgesia observed in MTrSs, contributing to chronic pain.
