Abstract
TRPV family, identified as thermosensitive, Ca2+-permeable channels, consists of six subtypes. TRPV3 and 4 were described as heat transducers operative at moderately warm temperatures (>34 °C), whereas TRPV1 is activated by temperature above 42 °C. In natural environment, infrared light is detected as thermal radiation through skin. TRPV3 and 4 were reported to express in keratinocytes. They might, therefore, respond to infrared radiation and transfer the thermal signal to CNS. In this study, we examined the role of TRPV4 in regulation of body temperature by using transgenic mice defecting in TRPV4 protein. As thermal stimulus, infrared laser irradiation (λ=830 nm, 150 or 300 mW, 15 min) was applied to the back skin of the mouse, and temperatures of both skin surface and rectum were monitored. In wild type mouse, laser radiation which caused the increase in skin temperature up to 55 °C did not induce the change in body temperature. In TRPV4-knockout mice, however, moderate thermal stimulus, which increased the skin temperature less than 43 °C, resulted in the increase in the body temperature during the laser irradiation suggesting the loss of autonomic temperature regulation. The processing of moderate thermal radiation may partly depend on the TRPV4 expressed in skin cells. [J Physiol Sci. 2006;56 Suppl:S152]
