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TRPA 1 contributes to capsaicin‐induced facial cold hyperalgesia in rats
Author(s) -
Honda Kuniya,
Shinoda Masamichi,
Furukawa Akihiko,
Kita Kozue,
Noma Noboru,
Iwata Koichi
Publication year - 2014
Publication title -
european journal of oral sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.802
H-Index - 93
eISSN - 1600-0722
pISSN - 0909-8836
DOI - 10.1111/eos.12157
Subject(s) - trpv , capsaicin , hyperalgesia , chemistry , transient receptor potential channel , nociceptor , endocrinology , trpv1 , stimulation , sensitization , medicine , anesthesia , nociception , neuroscience , receptor , biology
Orofacial cold hyperalgesia is known to cause severe persistent pain in the face following trigeminal nerve injury or inflammation, and transient receptor potential ( TRP ) vanilloid 1 ( TRPV 1) and TRP ankylin 1 ( TRPA 1) are thought to be involved in cold hyperalgesia. However, how these two receptors are involved in cold hyperalgesia is not fully understood. To clarify the mechanisms underlying facial cold hyperalgesia, nocifensive behaviors to cold stimulation, the expression of TRPV 1 and TRPA 1 in trigeminal ganglion ( TG ) neurons, and TG neuronal excitability to cold stimulation following facial capsaicin injection were examined in rats. The head‐withdrawal reflex threshold ( HWRT ) to cold stimulation of the lateral facial skin was significantly decreased following facial capsaicin injection. This reduction of HWRT was significantly recovered following local injection of TRPV 1 antagonist as well as TRPA 1 antagonist. Approximately 30% of TG neurons innervating the lateral facial skin expressed both TRPV 1 and TRPA 1, and about 64% of TRPA 1‐positive neurons also expressed TRPV 1. The TG neuronal excitability to noxious cold stimulation was significantly increased following facial capsaicin injection and this increase was recovered by pretreatment with TRPA 1 antagonist. These findings suggest that TRPA 1 sensitization via TRPV 1 signaling in TG neurons is involved in cold hyperalgesia following facial skin capsaicin injection.