Microwave-induced changes in nerve cells: effects of modulation and temperature

Helix aspersa neurons were irradiated with continuous-wave (CW) and noise-amplitude-modulated microwaves (carrier frequency 2450 MHz, 20% AM, 2 Hz-20 kHz) in a specially designed waveguide exposure system. Continuous-wave microwave irradiations were conducted at 8 degrees, 21 degrees, and 28 degrees C, while noise-modulated irradiation was performed at 21 degrees C. The results showed that exposure of snail neurons to CW microwaves for 60 min at 12.9 W/kg inhibited spontaneous activity and reduced input resistance at 8 degrees and 21 degrees C but not at 28 degrees C. The relative decrease in resistance at 21 degrees C was half that at 8 degrees C. Exposure of neurons to noise-modulated microwaves at 6.8 and 14.4 W/kg predominately caused excitatory responses characterized by augmented membrane resistance and the appearance of greater activity. The effect differed qualitatively from the inhibition observed with continuous, unmodulated microwave irradiation.