Muscle pain induced by static contraction is modulated by transient receptor potential vanilloid 1 and ankyrin 1 receptors

Abstract Molecular mechanisms involved in the development of muscle pain induced by static contraction are not completely elucidated. This study aimed to evaluate the involvement of the transient receptor potential vanilloid 1 (TRPV1) and the transient receptor potential ankyrin 1 (TRPA1) receptors expressed in peripheral and central terminals of primary afferents projected to gastrocnemius muscle and spinal cord in muscle pain induced by static contraction. An electrical stimulator provided the contraction of rat gastrocnemius muscle and mechanical muscle hyperalgesia was quantified through the pressure analgesimeter Randall-Selitto. AMG9810 and HC030031 were used. When administered in ipsilateral, but not contralateral gastrocnemius muscle, drugs prevented mechanical muscle hyperalgesia induced by static contraction. Similar results were obtained by intrathecal administrations. We propose that, in an inflammatory muscle pain, peripheral and central TRPV1 and TRPA1 work together to sensitize nociceptive afferent fibers, and that TRPV1 and TRPA1 receptors are potential target to control inflammatory muscle pain.

CARDIOVASCULAR RESPONSE TO STATIC AND DYNAMIC MUSCLE CONTRACTIONS AT EQUIVALENT TENSION-TIME INDICES / 体力科学

In the present study, we examined cardiovascular response to static and dynamic hand-grip exercise at equivalent work load (peak tension) and tension-time index (TTI, integrated tension for time) in healthy young (n=8) and elderly (n=8) males. Static and dynamic exercises were conducted for 75 s and 150 s at 30% of maximal voluntary contraction (MVC) and for 45 s and 90 s at 50%MVC, respectively. Arterial pressure was continuously measured on a beat basis. Blood pressure at the end of exercise and the magnitude of pressor response induced by exercise did not differ significantly between static and dynamic exercises at the two work loads. The magnitude of pressor response tended to depend on work load. These findings were the same in both age groups. Consequently, it was indicated that blood pressure responses to static and dynamic hand-grip exercise at equivalent work load and TTI did not differ both in young and elderly people. Furthermore, it was suggested that central command and muscle metabolite induced stimulation of the exercise pressor reflex during static and dynamic exercise were similar based on the results of relative perceived exertion and blood pressure response during post-exercise arterial occlusion.