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The effect of low-intensity broadband pulsed THz radiation in the range from 0.05 to 1.2 THz, with power from 0.25 to 11.6 μW, on the growth of neurites of spinal ganglia of (10−12)-day chick embryos has been investigated. An analysis of the 3-min irradiation with powers in this range has demonstrated both stimulating and suppressive effects of THz radiation on the proliferative activity of neurites. This effect manifests itself with a decrease in the THz radiation power.

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We investigated the change in the proliferative activity of spinal ganglia in an organotypic tissue culture exposed to pulses of broadband terahertz (THz) radiation with different power densities ( Fig.). In particular, a decrease in the THz radiation power causes first suppressive and then stimulating effect. We did not reveal any changes in the sample temperature under exposure to THz radiation. A comparison of our results with the data in the literature suggests that cellular growth can be stimulated via nonthermal mechanisms because the power density of the radiation used by us is fairly low. However, with allowance for the facts that the absorption peaks of water lie in the THz range and that cells consist mainly of water (80%), there may be microthermal effects, leading to local heating of cell elements; this process affects the cell metabolism and changes the functional regulation. Siegel and Pikov [17], who performed irradiation with the parameters closest to those used in our study (density powers 0.28, 0.74, and 0.56 μW/cm −2 and irradiation time 1min), revealed a change in the neuron action potential. Although the effect was observed at the same THz radiation frequency (0.06 THz), it cannot be interpreted unambiguously because both blocking and enhancement of action potential manifested themselves. The effect of THz irradiation is likely to be determined to a greater extent by the irradiation dose rather than the radiation frequency. Therefore, it is obviously expedient to continue this study in wider ranges of THz radiation power densities and irradiation times. Fig. Dependence of the area index for irradiated samples on the THz radiation power density References: 1. P.H. Siegel and V. Pikov, "Can Neurons Sense Millimeter Waves?" SPIE Photon. West. BiOS. 7562, 17 (2010).

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