Hypoalgesic effect of millimeter waves in mice: Dependence on the site of exposure

Based on a hypothesis of neural system involvement in the initial absorptio n and further processing of the millimeter electromagnetic waves (MW) signa l, we reproduced, quantitatively assessed and compared the analgesic effect of a single MW treatment, exposing areas of skin possessing different inne rvation densities. The cold water tail flick test (cTFT) was used to assess experimental pain in mice. Three areas of exposure were used: the nose, th e glabrous skin of the right footpad, and the hairy skin of the mid back at the level of T5-T10. The MW exposure characteristics were: frequency = 61. 22 GHz; incident power density = 15mW/cm(2); and duration = 15 min. The max imum hypoalgesic effect was achieved by exposing to MW the more densely inn ervated skin areas - the nose and the footpad. The hypoalgesic effect in th e cTFT after MW exposure to the murine back, which is less densely innervat ed, was not statistically significant. These results support the hypothesis of neural system involvement in the systemic response to MW.