IN-VITRO METAL INHIBITION OF N-METHYL-D-ASPARTATE SPECIFIC GLUTAMATE-RECEPTOR BINDING IN NEONATAL AND ADULT-RAT BRAIN

The in vitro effect of methyl mercury (MM) and lead (Pb) on N-methyl-D -aspartate (NMDA)-specific glutamate receptor binding in neonatal (10 days old) and adult rat brain was investigated. The cerebral cortex wa s isolated from the neonatal and adult male Sprague-Dawley rats and th e synaptic plasma membranes were prepared to study the NMDA-specific g lutamate receptor binding by using (H-3)-glutamic acid. The metal salt s such as methyl mercury chloride and lea acetate were used to study t he effect of MM and Pb. Both MM and Pb is significantly inhibited the receptor binding in neonatal and adult rat brain in a concentration-de pendent manner, MM (IC50:0.95 +/- 0.08 mu M) was more potent in inhibi ting the receptor binding that Pb (IC50:60 +/- 7 mu M) in neonatal rat brain. A similar high potency was observed for MM than Pb in adult ra t brain but the IC50 values are very high (70 +/- 6 mu M and 300 +/- 2 4 mu M respectively) indicating less effect compared to neonatal brain . The data suggest that NMDA-receptor binding was more sensitive to MM and Pb in neonatal brain than in adult. MM was more effective than Pb because of its more lipophilicity.