Influence of extremely low frequency magnetic fields on Ca2+ signaling and NMDA receptor functions in rat hippocampus

Extremely low frequency (ELF < 300 Hz) electromagnetic fields affect several neuronal activities including memory. Because ELF magnetic fields cause altered Ca2+ homeostasis in neural tissues, we examined their influence on Ca2+ signaling enzymes in hippocampus and related them with NMDA receptor functions. Hippocampal regions were obtained from brains of 21-day-old rats that were exposed for 90 days to 50 Hz magnetic fields at 50 and 100 μT intensities. In comparison to controls, ELF exposure caused increased intracellular Ca2+ levels concomitant with increased activities of Ca2+-dependent protein kinase C (PKC), cAMP-dependent protein kinase and calcineurin as well as decreased activity of Ca2+-calmodulin-dependent protein kinase in hippocampal regions. Simultaneous ligand-binding studies revealed decreased binding to N-methyl-d-aspartic acid (NMDA) receptors. The combined results suggest that perturbed neuronal functions caused by ELF exposure may involve altered Ca2+ signaling events contributing to aberrant NMDA receptor activities.