• Hiroshi Kamo, Kuniya Honda, Junichi Kitagawa, Yoshiyuki Tsuboi, Masahiro Kondo, Masato Taira, Akiko Yamashita, Narumi Katsuyama, Yuji Masuda, Takafumi Kato, and Koichi Iwata.
• Department of Oral and Maxillofacial Surgery, Nihon University School of Dentistry, Tokyo, Japan.
• J Oral Sci. 2008 Jun 1; 50 (2): 175-9.

AbstractRecent animal studies have demonstrated that many trigeminal ganglion neurons co-express TRPV1 and TRPA1 receptors following peripheral inflammation. In the present study, we examined whether cold receptors were sensitized by capsaicin in awake monkeys. Two monkeys were trained to detect a change in cold stimulus temperature (30 degrees C to 0.5, 1.0, 1.5 or 2.0 degrees C) applied to the facial skin. A total of 589 trials were studied, and the number of escape and hold-through trials and detection latency were measured. The number of escape trials was increased after capsaicin treatment, whereas that of hold-through trials was decreased. Detection latency was significantly decreased after capsaicin treatment. The present findings suggest that topical application of capsaicin to the facial skin induces reversible hypersensitivity to a facial cold stimulus in behaving monkeys.

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