Pulse Microwave Effects on Nerve Vitality

Isolated sciatic nerves of frogs were exposed to 2.45-GHz pulse-microwave radiation in a waveguide exposure system at an average specific absorption rate (SAR) of 10 mW/g. In previous studies using continuous-wave (cw) microwave radiation at an SAR of 10 mW/g, survival time of the irradiated nerve when stimulated to fire at a high rate (50 twin pulses per sec) was shortened significantly. This investigation was performed to determine if pulse-microwave radiation produced the same or different effects on the vitality of frog sciatic nerves as continuous-wave microwave radiation. Three sets of experiments were carried out using 10-μsec-wide pulses at 50 pps, with an average SAR of 10 mW/g: (1) asynchronous pulsing wherein the mw pulse was delivered at varying times in the firing cycle; (2) synchronous pulsing during the peak of the nerve action potential; and (3) synchronous pulsing during the quiescent period between nerve firings. In all three cases a significant decrease in the survival time of the exposed nerves, as compared to their unexposed mates, was seen. However, the magnitude of this effect was essentially the same in all three cases and was also comparable with the effect seen earlier using cw (of equivalent SAR).