AGE DOES NOT AFFECT THERMAL AND CARDIORESPIRATORY RESPONSES TO MICROWAVE-HEATING IN CALORICALLY RESTRICTED RATS

This study sought to determine whether age influences the thermal dist ribution and cardiorespiratory responses to 35 GHz microwave (MW) heat ing. Male Sprague-Dawley rats (n = 8/group) 3 to 4 mo old (young), 15 to 16 mo old (middle-aged), and 24 to 25 mo old (old) were used, All a nimals were restricted to 63% of ad libitum feed. Rats were anesthetiz ed (ketamine) and a catheter was placed into a carotid artery for meas urement of mean arterial blood pressure (MAP). Anesthetized rats were then exposed to MWs until death, while measuring MAP, heart rate and t emperatures at five sites (colonic, left and right tympanic, subcutane ous, and tail). Before MW exposure, there were no significant (p <.05) differences among age groups in measured parameters. MW produced incr eases in temperature at each of the measured sites; temperatures at de ath did not differ between groups, Hear? rate increased throughout MW exposure, in a statistically identical manner in all age groups. MAP w as initially well maintained and then, in the latter phases of heating , precipitously declined until death, with no discernible age-related difference. Respiration rate was not altered by MW exposure in any gro up. Finally, there were no group differences in the MW exposure time r equired to induce death. Thus, age does not alter thermal and cardiore spiratory responses to 35 GHz MW heating in food-restricted rats.