DOES NITRIC-OXIDE MEDIATE CIRCULATORY FAILURE INDUCED BY 35-GHZ MICROWAVE-HEATING

The purpose of this study was to determine whether nitric oxide (NO) c ontributes to the hypotensive state induced by exposure to radiofreque ncy radiation of millimeter-wavelength (MMW). This was accomplished us ing a synthetic analogue of L-arginine, N-omega-nitro-L-arginine methy l ester (L-NAME), to competitively inhibit NO synthesis. Ketamine-anes thetized rats were instrumented for the measurement of arterial blood pressure, EGG, and temperature at five sites. Animals were exposed to 35-GHz radiofrequency radiation until mean arterial pressure (MAP) dec reased to 75 mmHg. MMW exposure was then halted and either saline or L -NAME (1, 2.5, 5, or 10 mg/kg) was administered; each rat received onl y one dose. Following irradiation, L-NAME at each dose produced a peak increase in MAP that was smaller than that produced by the same dose of L-NAME in nonirradiated rats. There was no difference in post-MMW s urvival times between L-NAME- and saline-treated rats. These results i ndicate that bolus administration of L-NAME does not reverse hypotensi on induced by 35-GHz microwave heating, suggesting that excess levels of NO do not mediate this form of circulatory failure.