Millimeter wave effects on electrical responses of the sural nerve in vivo

Abstract

Millimeter wave (MMW, 42.25 GHz)-induced changes in electrical activity of the murine sural nerve were studied in vivo using external electrode recordings. MMW were applied to the receptive field of the sural nerve in the hind paw. We found two types of responses of the sural nerve to MMW exposure. First, MMW exposure at the incident power density >/=45 mW/cm(2) inhibited the spontaneous electrical activity. Exposure with lower intensities (10-30 mW/cm(2)) produced no detectable changes in the firing rate. Second, the nerve responded to the cessation of MMW exposure with a transient increase in the firing rate. The effect lasted 20-40 s. The threshold intensity for this effect was 160 mW/cm(2). Radiant heat exposure reproduced only the inhibitory effect of MMW but not the transient excitatory response. Depletion of mast cells by compound 48/80 eliminated the transient response of the nerve. It was suggested that the cold sensitive fibers were responsible for the inhibitory effect of MMW and radiant heat exposures. However, the receptors and mechanisms involved in inducing the transient response to MMW exposure are not clear. The hypothesis of mast cell involvement was discussed.

THz in biology and medicine: toward quantifying and understanding the interaction of millimeter- and submillimeter-waves with cells and cell processes

“…Similar results correlating millimeter wave exposure (62 and 75 GHz) and direct temperature rise were also reported for the changes induced in ionic currents in these neurons [10]. Most recently, the electrical response of an exposed frog sural nerve (>45mW/cm 2 at 42 GHz) showed threshold effects and transient behavior that were not well reproduced by broadband radiant heating [11]. Additional studies have focused on millimeter-wave induced changes in cell membrane permeability.…”

“…Civilian Federal Agencies, very few research groups are willing to undertake these studies. Several investigations [4][5][6][7][8][9][10][11][12][13][14][15][16], mainly outside the U.S., have noted significant impact on neuronal activity from modest level millimeter wave exposures (40-130 GHz, 1-100 mW/cm 2 , seconds to minutes) that are not much higher than the Federal Communications Commission-established maximum permissible exposure (MPE) limits of 1 mW/cm 2 for 6 minutes in the 30-300 GHz frequency regime [17]. Synchronization of the firing rate of neurons in the hypothalamus of both rabbit and rat was observed at and below 10 mW/cm 2 [4,5].…”

“…Even at 2-3mW/cm 2 , at certain frequencies between 40 and 52 GHz an isolated frog sciatic nerve showed measureable changes in the amplitude and latency of its compound action potential [7]. Higher levels of millimeter-wave power (10-100mW/cm 2 ), which tend to raise the temperature of the exposed sample, have been shown to produce changes in neuronal activity that sometimes do, and sometimes don't correlate with broadband radiant heating [8][9][10][11]. For example, changes in action potential firing rates in skate skin exposed to 130mW/cm 2 at 54 GHz were anticorrelated with those produced by radiant heating [8].…”

Whole‐genome expression analysis in primary human keratinocyte cell cultures exposed to 60 GHz radiation

“…TRPV2 is a widely expressed calcium channel. In neurons of the peripheral nervous system, TRPV2 is involved in heat sensing and has been proposed as a candidate for the mediation of MMW effects in pain therapy [Alekseev et al, 2010].…”

“…Furthermore, it was shown that MMW treatment may have an analgesic effect in both human and animal models [Radzievsky et al, 1999;Rojavin et al, 2000]. This hypoalgesia can result from a direct effect of MMW on nerve cells [Radzievsky et al, 2008;Alekseev et al, 2010].…”