Lack of effect of 50-Hz magnetic field exposure on the binding affinity of serotonin for the 5-HT 1B receptor subtype

There is some concern that exposure to extremely low-frequency magnetic fields (MF) causes adverse health effects via signal transduction pathways. Two previous studies reported that exposure to 50-Hz MF decreased the binding affinity of the 1B receptor subtype of serotonin (5-HT) in rat brain membranes. The aim of this study was to investigate whether the exposure to MF affects binding to the 5-HT1B receptor and a physiological function associated with 5-HT1B receptor activation. Rat brain crude membrane fractions, including 5-HT1B receptor and C6-glial cells transfected with human 5-HT1B receptor gene, were exposed to 50-Hz MF at 1 mT using Merritt coils under temperature-regulated conditions. In the rat crude membrane, there was no significant difference in the affinity constant of [H-3]-5-HT between exposed (K-d: 0.92 +/- 0.38 nM) and sham-exposed (K-d: 1.00 +/- 0.32 nM). The lack of affinity change after exposure was also confirmed using a chemical agonist of the 5-HT receptor, [H-3]-5-carboxytryptamine (K-d: 0.59 +/- 0.06 nM for exposed and 0.71 +/- 0.08 nM for sham). Similar negative results in terms of affinity constant were obtained on the human 5-HT1B receptor in C6-glial cells. In addition, forskolin-stimulated cAMP production was inhibited by 5-HT administration in a dose-dependent manner in C6-glial cells, but exposure did not modify the inhibitory response. This study thus failed to confirm the previous results and findings suggest that exposure to MF below the current occupational limit does not affect the physiological function involved in 5-HT1B receptor subtypes. (C) 2010 Elsevier B.V. All rights reserved.