Age-specific impairment of morris water maze performance following neonatal exposure to magnetic resonance image in rats.

To investigate the effects of magnetic resonance image (MRI) exposure on CNS development, we examined the effects of neonatal exposure of rats to a MRI magnetic field on their performance in the Morris water maze. After birth, all litters were randomly divided into an MRI-scanning group (experimental group) comprised of 7 mother rats and their offspring, and a control group, which consisted of the other 7 mothers and their pups. Newborn rat pups of MRI-scanning group were exposed to a 1.5 T magnetic resonance image (MRI) magnetic field for 7 days (postnatal day 1-day 7, 10 min/day). And behavioral tests were taken at 1st-, 2nd- and 5th-month after birth. At the age of 2 months postnatal, both male and female rats of the experimental groups made fewer crossings over the target area in the probe trial than did the control group. This result showed that the exposed animals represented a "reference memory" deficit, that is to say, these rats had a deficit ability to use environmental cues to locate the former position in space. No deficits were evident in the 1st- and 5th-month groups. These results demonstrate an age-specific cognitive/behavioral deficit induced by neonatal exposure to an MRI magnetic field. These findings indicate that the safety of MRI exposure must be considered with care and appropriate cautions should be taken.