An increase in cAMP concentration in mouse hippocampal slices exposed to low-frequency and pulsed magnetic fields

Our previous studies revealed that magnetic fields amplified evoked potentials recorded from mouse hippocampal slices. In search for the mechanism of this effect, we evaluated the concentration of cAMP in slices exposed to low-frequency and pulsed magnetic fields. Low-frequency magnetic fields of 15 mT applied at 0.16 Hz for 30 min enhanced the concentration of cAMP almost three-fold. The concentration of cAMP continued to rise through the first hour after turning magnetic fields off, reaching almost a four-fold increase, and then returned to control levels at the end of the second hour. Neither static magnetic fields nor magnetic fields applied with the frequency of 0.5 Hz had any effect on cAMP concentration. The increase in cAMP levels was dependent on the strength of the magnetic field and required the presence of extracellular calcium. A pulsed magnetic field applied with variable intensity (9-15 mT) and in cycles lasting from 5 to 20 min doubled the cAMP concentration. These results support our previous electrophysiological observations and provide biochemical correlates for their interpretation.