title: Effects of millimeter wave irradiation and equivalent thermal heating on the activity of individual neurons in the leech ganglion.
abstract: Many of today's radiofrequency-emitting devices in telecommunication, telemedicine, transportation safety, and security/military applications use the millimeter wave (MMW) band (30-300 GHz). To evaluate the biological safety and possible applications of this radiofrequency band for neuroscience and neurology, we have investigated the physiological effects of low-intensity 60-GHz electromagnetic irradiation on individual neurons in the leech midbody ganglia. We applied incident power densities of 1, 2, and 4 mW/cm(2) to the whole ganglion for a period of 1 min while recording the action potential with a standard sharp electrode electrophysiology setup. For comparison, the recognized U.S. safe exposure limit is 1 mW/cm(2) for 6 min. During the exposure to MMWs and gradual bath heating at a rate of 0.04°C/s (2.4°C/min), the ganglionic neurons exhibited similar dose-dependent hyperpolarization of the plasma membrane and decrease in the action potential amplitude. However, narrowing of the action potential half-width during MMW irradiation at 4 mW/cm(2) was 5 times more pronounced compared with that during equivalent bath heating of 0.6°C. Even more dramatic difference in the effects of MMW irradiation and bath heating was noted in the firing rate, which was suppressed at all applied MMW power densities and increased in a dose-dependent manner during gradual bath heating. The mechanism of enhanced narrowing of action potentials and suppressed firing by MMW irradiation, compared with that by gradual bath heating, is hypothesized to involve specific coupling of MMW energy with the neuronal plasma membrane.
authors.affiliation: Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California; Neural Engineering Program, Huntington Medical Research Institutes, Pasadena, California; and.
authors.forename: Sergii
authors.initials: S
authors.lastname: Romanenko
authors.affiliation: Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California;
authors.forename: Peter H
authors.initials: PH
authors.lastname: Siegel
authors.affiliation: Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California; Department of Biological Sciences, University of Cincinnati, Cincinnati, Ohio.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Wagenaar
authors.affiliation: Neural Engineering Program, Huntington Medical Research Institutes, Pasadena, California; and pikov@hmri.org.
authors.forename: Victor
authors.initials: V
authors.lastname: Pikov
mesh_terms: D000200:Action Potentials / Q000502:physiology / Q000528:radiation effects; D000818:Animals; D002462:Cell Membrane / Q000502:physiology / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D060733:Electromagnetic Radiation; D017952:Ganglia, Invertebrate / Q000502:physiology / Q000528:radiation effects; D006358:Hot Temperature; D007865:Leeches / Q000502:physiology* / Q000528:radiation effects*; D008839:Microelectrodes; D009474:Neurons / Q000502:physiology* / Q000528:radiation effects*
keywords: action potential; heating; leech ganglion; millimeter wave; thermal