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.
Keywords:
Muscle pain; Static contraction; TRPA1 and TRPV1 receptors
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A) Intramuscular administration of AMG9810 reduced the mechanical muscle hyperalgesia induced by static contraction when administered in the ipsilateral but not in the contralateral gastrocnemius muscle. The administration of AMG9810 in sham group did not affect the mechanical muscle withdrawal threshold. B) Intrathecal administration of AMG9810 reduced the mechanical muscle hyperalgesia induced by static contraction. The symbol “*” indicates responses significantly lower than that induced by static contraction (p < 0.05, ANOVA, Tukey test). Abbreviations: ct - contralateral.
A) Intramuscular administration of HC030031 reduced the mechanical muscle hyperalgesia induced by static contraction when administered in the ipsilateral but not in the contralateral gastrocnemius muscle. The administration of HC030031 in sham group did not affect the mechanical muscle withdrawal threshold. B) Intrathecal administration of HC030031 reduced the mechanical muscle hyperalgesia induced by static contraction. C) Dose-response analysis of the data for intramuscular administration of HC030031. D) Dose-response analysis of the data for intrathecal administration of HC030031. The symbol “*” indicates responses significantly lower than that induced by static contraction (p < 0.05, ANOVA, Tukey test). Abbreviations: ct - contralateral.