Effects of capsaicin and menthol on temperature sensation during CO2 water immersion

Abstract

It is known that CO₂ inhibits the activity of cold receptors and facilitates that of warm receptors of the skin. Thus, it is expected that thermal sensation was altered by CO₂ water immersion at the same water temperature compared with during fresh water immersion. We compared the effect of capsaicin and menthol applied topically to the forearm skin on temperature sensation score during the immersion of CO₂ (1000ppm) water and fresh water at 33°C for 10 min. Though slight pain occurred on the capsaicin site, temperature sensation score was ^"neutral^" before water immersion for each subject. The score shifted to the warmer sensation during CO₂ water immersion, whereas it remained ^"neutral^" or slightly shifted to the ^"warm^" during fresh water immersion. In the menthol application, a few subjects reported a ^"slightly cool^" sensation before water immersion. The score shifted to the cooler during fresh water immersion, whereas it remained ^"neutral^" or slightly shifted to the ^"warm^" during CO₂ water immersion. The change was remarkable in a later stage of the immersion. These results appear to suggest that capsaicin and menthol modify the changes in skin temperature sensation elicited by CO₂. [Jpn J Physiol 54 Suppl:S236 (2004)]