Inhibition of Muscular Nociceptive Afferents via the Activation of Cutaneous Nociceptors in a Rat Model of Inflammatory Muscle Pain
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Topical irritants such as capsaicin (CAP), peppermint oil (PO), and mustard oil (MO) are effective in relieving inflammatory muscle pain. We investigated the effects of topical irritants in a rat model of inflammatory muscle pain produced by injecting complete Freund’s adjuvant (CFA) into the tibialis anterior muscle. CFA-induced mechanical hypersensitivity and the spontaneous activity of muscular nociceptive afferents, and decreased weight-bearing of the hindlimb were relieved by topical application of CAP, PO, or MO on the skin overlying the inflamed muscle. The effects of topical irritants were abolished when applied to the skin on the ipsilateral plantar region or on the contralateral leg, or when the relevant cutaneous nerve or dorsal root was transected. Our results demonstrated that topical irritants may alleviate inflammatory muscle pain via activating cutaneous nociceptors and subsequently inhibiting the abnormal activity of muscular nociceptive neurons.
KeywordsInflammatory muscle pain Muscular nociceptor Cutaneous nociceptor Capsaicin
We thank Bo Yuan and Tao Wang from the Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Beijing, China, for technical assistance. This work was supported by the National Natural Science Foundation of China (81771205 and 91632113), the Natural Science Foundation and Major Basic Research Program of Shanghai Municipality, China (16JC1420500 and 16JC1420502), the Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences (2017-I2M-3-008), and the National Natural Science Foundation for Young Scientists of China (81600956).
Conflict of interest
All authors claim that there are no conflicts of interest.
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