Direct suppressive effects of weak magnetic fields (50 Hz and 16(2/3) HZ) On melatonin synthesis in the pineal gland of Djungarian hamsters (Phodopussungorus)

In many investigations performed thus far on rodents, a suppression of mela tonin synthesis was observed when animals were exposed to weak magnetic fie lds. However, among the several issues not yet resolved is the question of whether the observed changes are caused by direct effects on the pineal gla nd or by indirect effects, e.g., at the level of the eyes. We, therefore, p erformed a series of experiments in which direct effects of weak magnetic f ields were studied in isolated pineal glands of Djungarian hamsters (Phodop us sungorus). After sacrifice of animals during morning hours, pineal gland s were removed and placed individually into glass chambers that were perfus ed with oxygenated buffer. Experiments (n = 8) lasted for 8 hr. Magnetic fi elds (16(2/3) or 50 Hz at 86 mu Tesla) were generated by Helmholtz coils, a nd were present during the entire period. In each experiment, 12 exposed, a nd 12 sham-exposed, pineal glands were placed individually in glass chamber s, which were surrounded by identical coils. Because of the design of the c oils (bifilament), and the experimental setup (black box), the experimentat or was not aware which coil was activated until the results were obtained. After 3.25 hr of adaptation, melatonin production was stimulated by isoprot erenol (10(-7) M) for 30 min. fluted fractions were collected, and melatoni n concentrations were measured by radioimmunoassay. Maximum melatonin produ ction was achieved after 5-7 hr. In all experiments, maximum melatonin conc entrations were lower in the exposed groups compared with the sham-exposed controls. Statistical analyses for each frequency showed significant suppre ssive effects at 16(2/3) Hz (P < 0.01), and 50 Hz (P < 0.001). It is conclu ded that the suppressive effects of magnetic fields on the synthesis of mel atonin are a result of primary mechanisms at the level of the pineal gland.