Temperature and corticosterone relationships in microwave-exposed rats

Plasma corticosterone and colonic temperature were measured in unanesthetized male rats exposed to 2,450-MHz continuous wave (cw) radiation to characterize the response of the pituitary-adrenal axis to microwave exposure. The rats were exposed in the far field of a horn antenna for 30 or 60 min at power densities of 0, 13, 20, 30, 40, 50, or 60 mW/cm2, or for 120 min at 0, 13, 20, 30, or 40 mW/cm2. The average energy absorption rate of the rats was 0.16 W/kg absorbed per mW/cm2 incident. Plasma from individual rats decapitated immediately after exposure was collected for analysis. Colonic temperature was significantly elevataed after exposures to power densities of 13 mW/cm2 or greater, with progressively larger increases after high intensity exposures. Plasma corticosterone was significantly elevated above control levels only after exposures at 50 or 60 mW/cm2 for 30- or 60-min exposures, and at 20, 30, and 40 mW/cm2 for 120-min exposures. The relationship between the increased levels of circulating corticosterone and colonic temperature suggested that the increases in corticosterone levels may reflect a level of physiological response to the body temperature elevations caused by microwave exposure.