We have previously identified Ntan1 as a magnetism response gene by differential display screening in cultured rat hippocampal neurons. Ntan1 mRNA was ubiquitously expressed in all the mouse tissues examined but relatively abundant in brain, retina and testis. Ntan1 mRNA expression was detectable in the embryonic 12-day mouse brain and gradually increased with ageing. In situ hybridization analysis showed high localization of Ntan1 mRNA in pyramidal cell layer of CA region and granular cell layer of dentate gyrus in the hippocampus, and Purkinje and granular cell layers in the cerebellum, respectively. Ntan1 mRNA expression was significantly increased about two-fold 12 h after brief exposure for 15 min to magnetism at 100 mT with a gradual decrease thereafter in cultured mouse hippocampal neurons. When embryonic 12-day-old or newborn mice were successively exposed to magnetic fields at 100 mT for 2 h, four times per day until the postnatal seventh day, Ntan1 mRNA was significantly increased about 1.5-2-fold in the hippocampus in vivo. The mice exposed to magnetic fields under the same condition showed significantly decreased locomotor activity. These results suggest that magnetic exposure affects higher order neural functions through modulation of genes expression.