Influence of 50 Hz magnetic fields on circadian rhythm of the suprachiasmatic nucleus activity

Extremely low frequency (ELF) magnetic fields (MF), such as 50 Hz or 60 Hz magnetic fields, have been shown to suppress the nocturnal production of pineal melatonin. The amount of melatonin produced in the pineal gland changes according to the circadian rhythm. The suprachiasmatic nuclei (SCN) of anterior hypothalamus are supposed to be the site of a master circadian pacemaker in mammals. The sympathetic neurons that innervate the pineal gland are driven by the intrinsic activity of SCN. The study reported here is the first attempt to investigate whether the 50 Hz magnetic field exposure has any effects on the circadian rhythm generated in SCN itself. The results of this study indicated that 50 Hz magnetic field could influence the circadian rhythm generated in the SCN only when the direction of the field was in the horizontal plane of the rat brain.