Two previous studies (Massot et al. 2000 and Espinosa et al. 2006) reported that exposure to a 50 Hz magnetic field decreased the binding affinity of the 1B receptor subtype of serotonin (5-HT) in rat brain membranes. The aim of this study was to confirm whether the exposure to magnetic fields affects binding to the 5-HT1B receptor and a physiological function associated with 5-HT1B receptor activation.
Not only the protocol of Massot et al. 2000 was used, but also two additional protocols for binding experiments. Additionally, a physiological function activated via the 5-HT1B receptor (inhibition of cAMP production) was assayed.
In additional experiments, 8-OH was used to prevent binding of [³H]5-HT to 5-HT1A receptor and 5-CT was used to prevent binding to 5-HT1B receptor.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
50 Hz
Exposure duration:
continuous for 60 min
|
|
| Frequency | 50 Hz |
|---|---|
| Type | |
| Exposure duration | continuous for 60 min |
| Exposure source | |
|---|---|
| Setup | two sets of Merritt coils produced a field uniform within 2% in a 20 cm x 20 cm exposure area inside each coil system; samples placed in plates with 96- or 24-wells located in temperature-controlled containers which were placed inside each coil |
| Sham exposure | A sham exposure was conducted. |
| Measurand | Value | Type | Method | Mass | Remarks |
|---|---|---|---|---|---|
| magnetic flux density | 1.1 mT | effective value | measured | - | - |
In the rat membrane, there was no significant difference in the binding affinity constant of [³H]5-HT to the receptor between exposed and sham exposed membranes. The lack of binding affinity change after exposure was also confirmed using a chemical agonist of the 5-HT receptor, [³H]5-CT.
Similar negative results in terms of binding affinity constant were obtained on the human 5-HT1B receptor in C6 cells.
In addition, forskolin-stimulated cAMP production was inhibited by 5-HT administration in a dose-dependent manner in C6 cells, but exposure did not modify the inhibitory response.
These findings thus failed to confirm the data of the previous studies and suggest that exposure to a magnetic field below the current occupational exposure limit does not affect the physiological function involved in 5-HT1B receptor subtypes.
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