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.
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).
| Exposure | Parameters |
|---|---|
|
Exposure 1:
5–100 Hz
Exposure duration:
intermittent, 1 s on/1 s off, repeated 5 times
intracellular recordings
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Exposure 2:
5–100 Hz
Exposure duration:
intermittent, 10 s on/30 s off, repeated 5 or 20 times
network oscillations
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|
Exposure 3:
16–50 Hz
Exposure duration:
not clearly indicated
optical recordings
|
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Previous experiments on DC fields [Bikson et al., 2004] were repeated and extended to AC fields.
| 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 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. |
| 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 |
| 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 source |
|
|---|---|
| Additional info | Measurements were averaged over five repeats at each frequency and field strength (20 repeats for fields up to 2 V/m). |
| 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 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. |
| 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 |
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.
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