SEARCH FOR FREQUENCY-SPECIFIC EFFECTS OF MILLIMETER-WAVE RADIATION ONISOLATED NERVE FUNCTION

Effects of a short-term exposure to millimeter waves (CW, 40-52 GHz, 0 .24-3.0 mW/cm(2)) on the compound action potential (CAP) conduction we re studied in an isolated frog sciatic nerve preparation. CAPs were ev oked by either a low-rate or a high-rate electrical stimulation of the nerve (4 and 20 paired pulses/s, respectively). The low-rate stimulat ion did not alter the functional state of the nerve, and the amplitude , latency, and peak latency of CAPs could stay virtually stable for ho urs. Microwave irradiation for 10-60 min at 0.24-1.5 mW/cm(2), either at various constant frequencies or with a stepwise frequency change (0 .1 or 0.01 GHz/min), did not cause any detectable changes in CAP condu ction or nerve refractoriness. The effect observed under irradiation a t a higher field intensity of 2-3 mW/cm(2) was a subtle and transient reduction of CAP latency and peak latency along with a rise of the tes t CAP amplitude. These changes could be evoked by any tested frequency of the radiation; they reversed shortly after cessation of exposure a nd were both qualitatively and quantitatively similar to the effect of conventional heating of 0.3-0.4 degrees C. The high-rate electrical s timulation caused gradual and reversible decrease of the amplitude of conditioning and test CAPs and increased their latencies and peak late ncies. These changes were essentially the same with and without irradi ation (2.0-2.7 or 0.24-0.28 mW/cm(2)), except for attenuation of the d ecrease of the test CAP amplitude. This effect was observed at both fi eld intensities, but was statistically significant only for certain fr equencies of the radiation. Within the studied limits, this effect app eared to be dependent on the frequency rather than on the intensity of the radiation, but this observation requires additional experimental confirmation. (C) 1997 Wiley-Liss, Inc.