[The influence of geomagnetic field variations on the pineal gland circadian activity].

Daily changes of geomagnetic field (GMF) of the Russian northwest region were studied in different seasons of years with high and low sun activities. It was shown that Ki-indexes of GMF-activities had minimal values at 4-5 h of UT, as a peak of maximum was at 20-21 h of UT in winter but in summer it shifted to 14-15 h UT. It has been suggested that the level of GMF in the environment influences the processes with nitric oxide participation, which effects on the melatonin production by pineal gland. GMF, along with illumination, take part in circadian activity of pineal gland.