To study the effects of a pulsed electromagnetic field exposure on adenosine recptors A1 and A2A in the rat cerebral cortex and cortical neurons.
Adenosine, an endogenous modulator of a wide range of biological functions, interacts with at least four cell surface receptor subtypes (as A1, A2A, A2B and A3 adenosine receptors). A1 and A2A adenosine receptors are highly expressed in the central nervous system compared to the other receptor subtypes.
The brain, cerebral cortex and membranes were prepared from male Sprague-Dawley rats.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
75 Hz
Modulation type:
pulsed
Exposure duration:
continuous for 2 h, 4 h, 6 h or 8 h
|
|
|
Exposure 2:
75 Hz
Modulation type:
pulsed
Exposure duration:
continuous for 2 h, 4 h, 6 h or 8 h
|
|
| Frequency | 75 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | continuous for 2 h, 4 h, 6 h or 8 h |
| Modulation type | pulsed |
|---|---|
| Pulse width | 1.3 ms |
| Duty cycle | 0.1 % |
| Exposure source |
|
|---|---|
| Setup | pair of rectangular horizontal coils (14 cm x 23 cm), each made of 1400 turns of copper wire placed opposite to each other; the biological samples (culture in flasks (9,2 cm x 8,2 cm with 10 ml of medium) or brain in a beaker (containing physiological oxygenated buffer)) were placed between the coils, so that the plane of the coils was perpendicular to the culture flasks |
| Sham exposure | A sham exposure was conducted. |
| Additional info | coils were powered by a PEMF generator system |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 1.5 mT | peak value | measured | - | ± 0,2 mT (in air at the level of the biological samples) |
| Frequency | 75 Hz |
|---|---|
| Type | |
| Waveform | |
| Exposure duration | continuous for 2 h, 4 h, 6 h or 8 h |
| Modulation type | pulsed |
|---|---|
| Pulse width | 1.3 ms |
| Duty cycle | 0.1 % |
| Exposure source |
|
|---|---|
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 3 mT | peak value | measured | - | ± 0,2 mT (in air at the level of the biological samples) |
Affinity values were not affected by pulsed electromagnetic field (PEMF) exposure, either at 1.5 or 3 mT. The PEMF exposure of the intact rat cerebral cortex or cortical neurons at 1.5 mT mediated a transient and significant increase in A2A adenosine receptors density after 4 h and 6 h of exposure and returned to values similar to controls after 8 h. In addition, PEMF exposure of the cerebral cortex and cortical neurons at 3 mT upregulated A2A adenosine receptors after 2 h and 4 h. The exposure of cortex membranes at 1.5 and 3 mT induced an increase in A2A adenosine receptor density after 2 h and was constant at all exposure times investigated.
PEMF exposure did not modify binding parameters of A1 adenosine receptors, such as affinity and density at 1.5 or 3 mT.
In cortical neurons, mRNA levels of A1 and A2A adenosine receptors were not affected by PEMF exposure for the times and intensities investigated. These results suggest that the PEMF-induced alteration of A2A adenosine receptors comprises the expression of receptors at the surface of the cell membrane, but not the transcriptional level.
In conclusion, the data clearly suggest a time and intensity-dependent effect of PEMFs on A2A adenosine receptors density in rat brain and cortical neurons. The PEMF-mediated upregulation of A2A adenosine receptors was constant in brain membranes and transient in the whole brain or intact cortical neurons.
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