| 2466 Intramuscular Blood Flow During Sub-maximal Contraction in Painful Human Masseter | ||
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T. ARIMA1, S. MINAGI1, L. ARENDT-NIELSEN2, and P. SVENSSON3, 1Okayama University, Graduate School of Medicine and Dentistry, Japan, 2Aalborg University, Center for Sensory-Motor Interaction, Denmark, 3Aarhus University, Clincal Oral Physiology, Denmark Objectives: There is little information on intramuscular blood flow during isometric contractions in painful human masseter. The aim of this study was to measure masseter blood flow in relation to different low-levels isometric contractions before and after experimentally-induced muscle pain. Methods: Eight healthy men (22-31 years) participated. They performed isometric masseter muscle contractions at 5%, 15%, and 25% of their maximal voluntary contraction (MVC) guided by feedback from surface electromyography (EMG) signals. Contractions lasted 30 s and were followed by 5 min rest. After the 3 contractions, capsaicin (0.1mL, 100mg/ml) was injected into right masseter to evoke deep pain. When the pain sensation had disappeared, the 3 levels of contractions were repeated. Laser Doppler Flowmetry (LDF) was used to assess blood flow and one single-fiber intramuscular probe was inserted into right masseter close to the injection site for continuous measurement. The data were processed in 30 s bins and the effects of contraction (before and during), contraction level (5%, 15%, 25%) and pain (before and after injection) were tested with repeated measures ANOVAs. Results: Analysis of the LDF data did not show any significant effect of contraction (P > 0.798), contraction level (P > 0.053) or pain (P > 0.471). As expected the EMG data was significantly influenced by contraction (P < 0.003) and contraction level (P < 0.001) but not by painful injection due to the feedback (P > 0.056). Conclusions: Changes in blood flow could be one important factor in the pathophysiology of muscle pain. However, the present methods were unable to detect changes in blood flow related to contraction or contraction levels and a robust nociceptive input generated by the capsaicin did not change blood flow. Further studies will be necessary to clarify the importance of blood flow changes in relation to jaw muscle function during pain. | ||
| Seq #248 - Orofacial Sensory Motor Function 10:15 AM-11:30 AM, Friday, 12 March 2004 Hawaii Convention Center Exhibit Hall 1-2 | ||
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