Effects of postnatal exposure to methylmercury on spatial learning and memory and brain NMDA receptor mRNA expression in rats.
The extreme vulnerability of developing nervous system to methylmercury (MeHg) is well documented. Still unclear is the consequence of different postnatal period exposure to MeHg. We investigated the critical postnatal phase when MeHg induced neurotoxicity in rats and the underlying mechanism. Rats were given 5mg/(kg day) methylmercury chloride (MMC) orally on postnatal day (PND) 7, PND14, PND28, and PND60 for consecutive 7 days. A control group was treated with 0.9% sodium chloride solution 5 ml/(kg day) instead. On PND69, spatial learning and memory was evaluated by Morris water maze test. Behavior deficits were found in MMC-treated rats of PND7 and PND14 groups (p<0.01). N-methyl-D-aspartate (NMDA) receptor 2 subunits mRNA expressions were evaluated 3 days after the last administration. In hippocampus, the mRNA expression of NR2A and NR2B decreased, but the NR2C expression increased in PND14 group following MMC-treatment (p<0.01). In cerebral cortex, mRNA expression of NR2A decreased, with NR2C expression elevating in PND14 group following MMC-treatment (p<0.05). These observations suggest that the postnatal exposure to MeHg during PND7-20 could cause neurobehavioral deficits which extend to adulthood. Furthermore, the abnormal expression of NMDAR 2 subunits might associate with the impairment.
Liu
Wenjun
W
MOE Key Laboratory of Environment & Health, Institute of Environmental Medicine, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Hangkong Road 13, Wuhan, Hubei, PR China. liuwenjun-wh@163.com
Wang
Xinmei
X
Zhang
Rong
R
Zhou
Yikai
Y
D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism; D004785:Environmental Pollutants / Q000493:pharmacokinetics / Q000633:toxicity*; D005260:Female; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D008297:Male; D018782:Maze Learning / Q000187:drug effects*; D008568:Memory / Q000187:drug effects*; D008767:Methylmercury Compounds / Q000493:pharmacokinetics / Q000633:toxicity*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000096:biosynthesis*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013037:Spatial Behavior / Q000187:drug effects*; D013550:Swimming
D004785:Environmental Pollutants; D008767:Methylmercury Compounds; D012333:RNA, Messenger; D016194:Receptors, N-Methyl-D-Aspartate; C004925:methylmercuric chloride