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.