Topical capsaicin application causes cold hypersensitivity in awake monkeys.
Recent 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.
Kamo
Hiroshi
H
Department of Oral and Maxillofacial Surgery, Nihon University School of Dentistry, Tokyo, Japan.
Honda
Kuniya
K
Kitagawa
Junichi
J
Tsuboi
Yoshiyuki
Y
Kondo
Masahiro
M
Taira
Masato
M
Yamashita
Akiko
A
Katsuyama
Narumi
N
Masuda
Yuji
Y
Kato
Takafumi
T
Iwata
Koichi
K
D000279:Administration, Cutaneous; D000818:Animals; D002211:Capsaicin / Q000008:administration & dosage / Q000494:pharmacology*; D003080:Cold Temperature; D005145:Face / Q000294:innervation; D008251:Macaca; D011930:Reaction Time / Q000187:drug effects; D018689:Sensory System Agents / Q000008:administration & dosage / Q000494:pharmacology*; D012684:Sensory Thresholds / Q000187:drug effects*; D012867:Skin / Q000187:drug effects / Q000294:innervation; D050916:TRPV Cation Channels / Q000187:drug effects; D013823:Thermoreceptors / Q000187:drug effects*; D014851:Wakefulness
D018689:Sensory System Agents; D050916:TRPV Cation Channels; D002211:Capsaicin