First to determine if the thermoregulatory responses of the immature rat (6-7 days of age) to selected ambient temperatures change following repeated exposure to different intensities of cold stress and then to assess the consequences of simultaneous low-level microwave irradiation. Exposures were conducted at ambient temperatures which represent different levels of cold stress for the immature rat (ie, "exposure" ambient temperature = 20 and 30°C). Measurements of metabolic rate, colonic temperature, and tail skin temperature were made at "test" ambient temperatures of 25.0, 30.0, 32.5, and 35.0°C (tests were conducted at 5-6 and 16-17 days of age to determine pre- and postexposure responses).
|power density||50 W/m²||unspecified||measured||-||-|
Mean growth rates were lower for animals exposed to ambient temperature of 20°C than for those exposed to ambient temperature of 30°C, but microwave exposure exerted no effect at either exposure ambient temperature. Metabolic rates and body temperatures of all exposure groups were similar to values for untreated animals at test ambient temperature of 32.5°C and 35.0°C. Colonic temperatures of animals repeatedly exposed to sham or microwave conditions at exposure ambient temperature of 20°C or to sham conditions at exposure ambient temperature of 30°C were approximately 1°C below the level for untreated rats at test ambient temperature of 25.0°C and 30.0°C. However, when the exposure ambient temperature was warmer, animals exhibited a higher colonic temperature at these cold test ambient temperature, indicating that the effectiveness of low-level microwave treatment to alter thermoregulatory responses depends on the magnitude of the cold stress.