Magnetic field effects on pineal N-acetyltransferase activity and melatonin content in the gerbil--role of pigmentation and sex.

The ambient geomagnetic field influences a variety of biological phenomena. Electrical and biochemical parameters of the rodent pineal gland are influenced by the alteration of weak magnetic fields (MF), the magnetic receptor probably residing in the retina. However, open questions concern the role of retinal pigmentation as well as species- and sex-specific differences in MF perception. We therefore exposed male and female naturally pigmented and albino Mongolian gerbils, as well as Sprague-Dawley (SD) rats to a 60 degrees rotation of the horizontal component of the ambient MF. Alteration of nocturnal pineal melatonin content and N-acetyltransferase (NAT) activity were utilized as a parameter for assessing magneto-sensitivity. In pigmented gerbils, MF exposure resulted in no significant changes in pineal melatonin synthesis. In contrast, albino gerbils and SD rats exhibited--regardless of sex--significant decreases in pineal NAT activity and melatonin content following MF exposure. These results suggest that in rodents hypopigmentation appears to favor magnetoperception. The available evidence indicates that the pigmentation of the retina could play a crucial role.