Interstitial concentration of serotonin is increased in myalgic human trapezius muscle during rest, repetitive work and mental stress – an in vivo microdialysis study

Abstract

Objectives. The pathophysiology of trapezius myalgia is not fully elucidated. Serotonin (5-HT) is involved in modulation of nociception and hyperalgesia. Our aim was to compare the interstitial 5-HT levels of the trapezius muscle in women with chronic trapezius myalgia and in pain-free controls. Materials and methods. Microdialysate of the trapezius muscle collected every 20 minutes during rest, work (100 min) and stress (20 min) was used to study the dynamics of 5-HT in women with chronic trapezius myalgia (MYA; n=18) and in pain-free controls (CON; n=30). Results. MYA had higher levels of 5-HT than CON at baseline, during repetitive work, during mental stress and during recovery. There were no significant time effects on 5-HT levels. Conclusion. 5-HT has the potential of a biomarker of chronic myalgia. Elevated levels of 5-HT may be involved in maintenance of habitual chronic pain and might contribute to increased pain during exercise by facilitating the effect of released algesic substances linked to such muscle demands.

Key Words::

• Myalgia
• exercise
• mental stress
• serotonin
• microdialysis

Acknowledgements

The authors gratefully thank Dr Ingibjörg Jonsdottir for valuable advice.

Source of grant support: The Swedish Research Council (K2005-27x-15316-01A) and the Swedish Council for Working life and Social Research (2004–0289).

Declaration of interest: The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper.