Mercury vapor uptake into the nervous system of developing mice

The localisation of mercury in the developing nervous system following merc ury vapor (Hg-0) exposure is not clear. We therefore looked for mercury in the mouse nervous system following fetal or neonatal exposure to Hg-0. Mice were exposed to 50 or 500 mug/m(3) Hg-0 for 4 h a day for 5 days in late p regnancy, and pups sacrificed on postnatal day (P)1 or P40. Neonatal mice w ere exposed to 500 mug/ m(3) Hg-0 for 2 h between p1 and P23, and were sacr ificed 2 days later or at P40. Paraffin sections of the nervous system were stained with autometallography to detect inorganic mercury. No mercury was seen in the nervous system of pups after fetal exposure to the 50 mug/m(3) Hg-0 dose rate. After fetal exposure to the 500 mug/m(3) Hg-0 dose rate, m ercury was seen in nervous system blood vessels and sensory ganglia. No mer cury was seen in the nervous system after neonatal exposure to 500 mug/m(3) Hg-0 for 2 h between p1 and P10. From this exposure at P11 onwards, mercur y was detected in motor neurons. The lack of stainable mercury in early dev eloping central neurons suggests that the fetal and neonatal nervous system s are somehow protected from Hg-0 uptake. (C) 2001 Elsevier Science Inc. Al l rights reserved.