Effects of moderate static magnetic fields on the voltage-gated sodium and calcium channel currents in trigeminal ganglion neurons

Aim: To study the effects of static magnetic fields (SMF) on the electrophysiological properties of voltage-gated sodium and calcium channels on trigeminal ganglion (TRG) neurons. Methods: Acutely dissociated TRG neurons of neonatal SD rats were exposed to 125-mT and 12.5-mT SMF in exposure devices and whole-cell patch-clamp recordings were carried out to observe the changes of voltage-gated sodium channels (VGSC) and calcium channels (VGCC) currents, while laser scanning confocal microscopy was used to detect intracellular free Ca2+ concentration in TRG neurons, respectively. Results: (1) No obvious change of current–voltage (I–V) relationship and the peak current densities of VGSC and VGCC currents were found when TRG neurons were exposed to 125-mT and 12.5-mT SMF. However, the activation threshold, inactivation threshold and velocity of the channel currents above were significantly altered by 125-mT and 12.5-mT SMF. (2) The fluctuation of intracellular free Ca2+ concentration within TRG neurons were slowed by 125-mT and 12.5-mT SMF. When SMF was removed, the Ca2+ concentration level showed partial recovery in the TRG neurons previously exposed by 125-mT SMF, while there was a full recovery found in 12.5-mT-SMF-exposed neurons. Conclusions: Moderate-intensity SMF could affect the electrophysiological characteristics of VGCS and VGCC by altering their activation and inactivation threshold and velocity. The fluctuations of intracellular free Ca2+ caused by SMF exposure were not permanent in TRG neurons.