Magnetic field effects on pineal gland melatonin synthesis: comparative studies on albino and pigmented rodents.

Previous investigations have shown that the inhibitory effects of an earth-strength magnetic field on albino rat pineal melatonin synthesis is dependent on optic input. The possibility that ocular pigmentation might play a role in mammalian magnetosensitivity was explored in the present study by comparing hooded rat and golden hamsters with albino rats. Pineal melatonin synthesis, i.e. N-acetyl-transferase activity and melatonin content, was utilized as a parameter for assessing magnetosensitivity. In both rat strains nocturnal pineal melatonin synthesis was markedly inhibited following a single 30-min magnetic field stimulus consisting of a 50 degree rotation of the earth's field horizontal component. However, golden hamsters did not respond to the same magnetic stimulus, indicating a species-specific magnetosensitivity that is apparently independent of ocular pigmentation. Possible reasons for these differences are discussed.