Study type: Medical/biological study (experimental study)

Sensitivity of coherent oscillations in rat hippocampus to AC electric fields. med./bio.

Published in: J Physiol 2007; 583 Pt 2: 555-565

Aim of study (acc. to author)

This study was conducted to investigate the effects of electric fields with different frequencies on membrane potentials and coherent network oscillations in the brain of rats.

Background/further details

The brains were taken from adult male Sprague-Dawley rats (150-250 g). Kainic acid (glutamine like herbal agent) was applied to induce coherent network oscillations in the beta wave and gamma wave (15-100 Hz).

Endpoint

Exposure

Exposure Parameters
Exposure 1: 5–100 Hz
Exposure duration: intermittent, 1 s on/1 s off, repeated 5 times
intracellular recordings
Exposure 2: 5–100 Hz
Exposure duration: intermittent, 10 s on/30 s off, repeated 5 or 20 times
network oscillations
Exposure 3: 16–50 Hz
Exposure duration: not clearly indicated
optical recordings

General information

Previous experiments on DC fields [Bikson et al., 2004] were repeated and extended to AC fields.

Exposure 1

Main characteristics
Frequency 5–100 Hz
Type
Waveform
Exposure duration intermittent, 1 s on/1 s off, repeated 5 times
Additional info intracellular recordings
Additional info intracellular recordings
Exposure setup
Exposure source
Distance between exposed object and exposure source 6 mm
Setup Brain slices were placed in an interface recording chamber, perfused with artificial cerebrospinal fluid (aCSF), with the pyramidal layer perpendicular and the axis of the pyramidal cells' dendrites parallel to the electric field that was generated by chlorided silver electrodes, 2 mm in diameter and 45 mm long, located at the sides of the well, about 6 mm from the slice and parallel to the aCSF flow.
Additional info Measurements were averaged over five repeats at each frequency and field strength.
Parameters
Measurand Value Type Method Mass Remarks
electric field strength 16 V/m peak-to-peak value calibration - 0.5, 1, 2, 3, 5, 10, 16 V/m
electric field strength 5.65 V/m effective value calibration - 0.177, 0.354, 0.708, 1.41, 2.12, 3.54, 5.65 V/m

Exposure 2

Main characteristics
Frequency 5–100 Hz
Type
Waveform
Exposure duration intermittent, 10 s on/30 s off, repeated 5 or 20 times
Additional info network oscillations
Additional info network oscillations
Exposure setup
Exposure source
Additional info Measurements were averaged over five repeats at each frequency and field strength (20 repeats for fields up to 2 V/m).
Parameters
Measurand Value Type Method Mass Remarks
electric field strength 16 V/m peak-to-peak value calibration - 0.5, 1, 2, 3, 5, 10, 16 V/m
electric field strength 5.65 V/m effective value calibration - 0.177, 0.354, 0.708, 1.41, 2.12, 3.54, 5.65 V/m

Exposure 3

Main characteristics
Frequency 16–50 Hz
Type
Waveform
Exposure duration not clearly indicated
Additional info optical recordings
Additional info optical recordings at DC, 16, and 50 Hz
Exposure setup
Exposure source
Setup The somato-dendritic axis was parallel to the electric field that was generated by sintered Ag-AgCl cylindrical pellet electrodes, 1 mm in diameter and 12 mm long, placed 4 mm apart.
Parameters
Measurand Value Type Method Mass Remarks
electric field strength 150 V/m peak-to-peak value calibration - -
electric field strength 75 V/m peak value calibration - DC

Reference articles

  • Bikson M et al. (2004): Effects of uniform extracellular DC electric fields on excitability in rat hippocampal slices in vitro.

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

The direct current electric fields changed transmembrane potentials in hippocampal neuron somata by 0.18 mV per V/m applied. Alternating sinusoidal electric fields had smaller effects on transmembrane potentials. The transmembrane potential dropped as an exponential decay function of frequency. Concerning neuronal network oscillations, alternating current electric fields of higher or equal 6 V/m peak to peak shifted the gamma peak in the power spectrum to centre on the applied field frequency or a subharmonic. The ability of applied alternating current fields to alter gamma oscillations had a well-defined threshold.

Study character:

Study funded by

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