Administration of a nitric oxide donor does not affect hypotension induced by 35-GHz microwave heating

Sustained whole body exposure to 35-GHz radiofrequency radiation produces localized hyperthermia and hypotension, leading to circulatory failure and death. We previously demonstrated that pressor responses to nitric oxide (NO) synthesis inhibition are reduced following 35-GHz microwave (MMW) heating, implying that NO levels might also be reduced. This study therefore sought to determine whether administration of S-nitroso-N-acetylpenicillamine (SNAP), a NO donor, influences MMW-induced hypotension in ketamine-anesthetized rats. First, rats were exposed to MMW until mean arterial pressure (MAP) fell to 75 mmHg. MMW exposure was then discontinued and either SNAP (300 micrograms/kg/h) or saline was infused. SNAP infusion affected neither the hypotension nor the survival time following MMW exposure. In a second protocol, SNAP (300 micrograms/kg/h) or saline was infused prior to and throughout MMW exposure, which was continued until death. SNAP infusion did not alter either the onset or the magnitude of terminal hypotension. Therefore, we conclude that exogenous NO does not affect cardiovascular responses to 35-GHz MMW heating.