title: Non-conductive and miniature fiber-optic imaging system for real-time detection of neuronal activity in time-varying electromagnetic fields.
abstract: Establishing an appropriate threshold value for neuronal modulation by time-varying electromagnetic field (EMF) exposure is important for developing international guidelines to protect against the potential health effects, and to design a variety of medical devices. However, it is technically difficult to achieve real-time detection of neuronal activity under repetitive and long-term exposure to EMF. For this purpose, we developed a non-conductive, miniature, and flexible fiber-optic imaging system that does not affect the electromagnetic noise, induction heating, or vibration in a high-intensity and repetitive time-varying EMF exposure. Using the proposed system, we succeeded at real-time detection of spontaneous Ca2+oscillations in single neuronal and glial cells, as well as synchronized bursting activities of multiple neuronal networks at a micrometer-scale and millisecond-order spatiotemporal resolution during long-term EMF exposure (sinusoidal wave, 20kHz, 8.6mT, >30min). The results indicated that short-term (<5min) exposure-related neuronal modulation was not detectable; however, long-term (15-30min) exposure was observed to depress neuronal activities. In addition, the simultaneous and real-time recording of neuronal activity and the environmental temperature revealed that the neuronal modulation was accompanied by a 0.5-1°C rise in the temperature of the culture medium induced by the heat generation of exposure coils. These findings suggest that our real-time imaging system can be used for precise evaluation of the threshold values and clarification of the mechanisms of neuronal modulation induced by time-varying EMF exposure.
authors.affiliation: Biological Environment Sector, Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Abiko-Shi, Chiba 270-1194, Japan. Electronic address: saito@criepi.denken.or.jp.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Saito
authors.affiliation: Biological Environment Sector, Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Abiko-Shi, Chiba 270-1194, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Takahashi
authors.affiliation: Department of Precision Engineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-Ku, Tokyo 113-8656, Japan.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Jimbo
authors.affiliation: Biological Environment Sector, Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Abiko-Shi, Chiba 270-1194, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nakasono
mesh_terms: D000818:Animals; D015374:Biosensing Techniques / Q000295:instrumentation; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D020013:Calcium Signaling; D002478:Cells, Cultured; D004574:Electromagnetic Fields; D004867:Equipment Design; D005336:Fiber Optic Technology / Q000295:instrumentation*; D009457:Neuroglia / Q000166:cytology* / Q000378:metabolism; D009474:Neurons / Q000166:cytology* / Q000378:metabolism; D061848:Optical Imaging / Q000295:instrumentation*; D017208:Rats, Wistar
chemical_list: D002118:Calcium
keywords: Fiber-optic imaging system; Long-term exposure; Neuronal modulation; Real-time detection; Thermal effect; Time-varying electromagnetic field