A pilot study of the millimeter-wavelenght radiation effect on synaptic transmission med./bio.

Effects of 41.34 GHz millimeter waves were investigated in the isolated hemisected frog spinal cord preparation. The aim of the study was to establish whether millimeter wave irradiation alters conduction in a polysynaptic pathway from dorsal root afferent fibers to efferent of respective ventral root.

Dorsal root was stimulated with single supra-maximal pulses every 30 s (20-30 V, 0.6 msec width) and ventral root responses were measured. Experiments began after 30-160 min of stabilization and lasted for 65 min. Each experiment included two identical 5 min exposures.

• isolated spinal cord of the bullfrog Rana catesbeiana

For the entire investigated group of 13 preparations (average value), the first irradiation increased the waveform changes by 14 %. Of this group, 9 preparations with the most pronounced reaction to the first millimeter wave exposure had no reaction to the second one. In contrast, the other four preparations with subtle or no effect of the first irradiation reacted strongly to the second exposure.
In conclusion, the effect of even a short millimeter wave irradiation is not limited to changes taking place during this irradiation. The aftereffect of the first exposure was not detectable by physiological indices, but manifested itself as a change in the sensitivity to the second exposure. The difference in the effect of two consequent and identical exposures infers that this effect was not caused by millimeter wave heating (the heating effect of the first and the second exposure was always the same) and involved regulatory physiological mechanisms, such as adaptation and sensitization.