Study type: Medical/biological study (experimental study)

Comparison between low-level 50 Hz and 900 MHz electromagnetic stimulation on single channel ionic currents and on firing frequency in dorsal root ganglion isolated neurons. med./bio.

Published in: Biochim Biophys Acta Biomembr 2006; 1758 (5): 597-605

Aim of study (acc. to author)

The aim of the study was a qualitative comparison, using the same preparation, patch-clamp unit, and experimental protocols, between the effects of two different electromagnetic field stimulations on the electrophysiological properties of isolated adult rat dorsal root ganglions.

Background/further details

In dorsal root ganglions the oscillation frequency of the membrane potential is correlated with the stimulus intensity. Cell firing establishment and modulation respond to a complex equilibrium of membrane ionic currents.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 50 Hz
Exposure duration: continuous for 30 min
Exposure 2: 900 MHz
Modulation type: CW
Exposure duration: continuous for 30 min
  • SAR: 1 W/kg unspecified

Exposure 1

Main characteristics
Frequency 50 Hz
Type
Waveform
Exposure duration continuous for 30 min
Additional info Reference article: R. Tonini, M.D. Baroni, E. Masala, M. Micheletti, A. Ferroni, M. Mazzanti, Calcium protects differentiating neuroblastoma cells during 50 Hz electromagnetic radiation, Biophys. J. 81 (2001) 2580-2589.
Exposure setup
Exposure source
Setup The experimental chamber was encircled with the coils. For control experiments the current flowing in the coil was zeroed by switching off the waves generator. During the entire exposure, the cells were observed on the inverted microscope.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 125 µT effective value measured - 0.48 mV/m induced EF

Exposure 2

Main characteristics
Frequency 900 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 30 min
Additional info Reference articles: 1) K.C. Garg Gupta, R. Bahl, P. Barthia, Microstrip Lines and Slotlines, 2nd ed. Artech House, Boston and London, 1996. 2) M. Liberti, F. Apollonio, A. Paffi, M. Pellegrino, G. D'Inzeo, A coplanar waveguide system for cell exposure during electrophysiological recordings, IEEE Microwave Theory and Techniques Symposium, Fort Worth, 2004.
Modulation
Modulation type CW
Exposure setup
Exposure source
Exposure room The exposure system based on coplanar waveguide consisting of an open propagating structure with a dielectric substrate on which three metallic strips are deposited. A glass was chosen as a dielectric substrate to replace the microscope head stage.
Additional info The direction of E-field was almost parallel to the Petri dish surface and perpendicular to the glass surface.
Parameters
Measurand Value Type Method Mass Remarks
SAR 1 W/kg unspecified calculated - -

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • before exposure
  • during exposure

Main outcome of study (acc. to author)

The data demonstrate that the firing rate of these sensory neurons can be modified by 50/60 Hz magnetic field but not by low level 900 MHz fields.
The action of the 50/60 Hz magnetic field was biphasic. At first, the number of action potentials increased in time. Following this early phase, the firing rate decreased more rapidly than in control conditions. The explanation can be found at the single-channel level: exposed dorsal root ganglion neurons acutely showed increased functionality of calcium channels. In parallel, a calcium-activated potassium channel was able to increase its mean open time.

Study character:

Study funded by

Related articles