Cardiovascular and thermal effects of microwave irradiation at 1 and/or 10GHz in anesthetized rats

Relatively large thermal gradients may exist during exposure of an animal t o microwaves (MWs), particularly at high frequencies. Differences in therma l gradients within the body may lead to noticeable differences in the magni tude of cardiovascular changes resulting from MW exposure. This study compa res the thermal distribution and cardiovascular effects of exposure to a si ngle MW frequency with effects of simultaneous exposure to two frequencies. Ketamine-anesthetized male Sprague-Dawley rats (n = 58) were exposed indiv idually to one of three conditions: 1-GHz, 10-GHz, or combined 1- and 10-GH z MWs at an equivalent whole-body specific absorption rate of 12 W/kg. The continuous-wave irradiation was conducted under far-field conditions with a nimals in E orientation (left lateral exposure, long axis parallel to the e lectric field) or in H orientation (left lateral exposure, long axis perpen dicular to the electric field). Irradiation was started when colonic temper ature was 37.5 degrees C and was continued until lethal temperatures were a ttained. Colonic, tympanic, left and right subcutaneous, and tail temperatu res, and arterial blood pressure, heart rate, and respiratory rate were con tinuously recorded. In both E and Il orientations, survival time (i.e., tim e from colonic temperature of 37.5 degrees C until death) was lowest in ani mals exposed at 1-GHz, intermediate in those exposed at 1- and 10-GHz combi ned, and greatest in the 10-GHz group (most differences statistically signi ficant). At all sites (with the exception of right subcutaneous), temperatu re values in the 1- and 10-GHz combined group were between those of the sin gle-frequency exposure groups in both E and H orientations. During irradiat ion, arterial blood pressure initially increased and then decreased until d eath. Heart rate increased throughout the exposure period. The general, ove rall patterns of these changes were similar in all groups. The results indi cate that no unusual physiological responses occur during multi-frequency M W exposure, when compared with results of single-frequency exposure. Publis hed 2000 Wiley-Liss, Inc.(dagger)