ABSTRACT
There is evidence that phosphorylation plays a crucial role in the regulation of the NMDA receptors in the brain. In this study we examined the effect of acute and chronic ethanol treatment on the phosphorylation of the R2B subunit of the NMDA receptors in fetal cortical neurons. Additionally, the effect of acute ethanol treatment on the phosphorylation of the R2B subunit in adult cerebral cortex and hippocampus was also examined. The results show that acute or chronic ethanol treatments did not affect the total phosphorylation of the R2B subunit in cortical neurons. In adult mice, we observed that acute ethanol treatment increased the tyrosine phosphorylation of the R2B subunit in hippocampus but not in cerebral cortex. We also observed that acute or chronic ethanol treatments did not alter the Fyn or Csk levels in cortical neurons. Although Fyn, but not Csk, was present in adult cerebral cortex, ethanol did not phosphorylate the R2B subunit in this region. Like ethanol, MK-801 (NMDA antagonist) did not affect the phosphorylation of the R2B subunit in cortical neurons. Taken together, these results suggest that acute and chronic ethanol and MK-801 treatments do not affect the phosphorylation of the R2B subunit in fetal cortical neurons and adult cerebral cortex. Based on these observations, we speculate that the R2B subunit of the NMDA receptors is regulated by multiple cascades and in a brain region specific manner.
Subject(s)
Cerebral Cortex/drug effects , Ethanol/pharmacology , Neurons/drug effects , Peptide Fragments/drug effects , Receptors, N-Methyl-D-Aspartate/drug effects , Animals , Cells, Cultured , Cerebral Cortex/cytology , Cerebral Cortex/metabolism , Dizocilpine Maleate/pharmacology , Excitatory Amino Acid Antagonists/pharmacology , Female , Hippocampus/cytology , Hippocampus/drug effects , Hippocampus/metabolism , Male , Mice , Mice, Inbred C57BL , Neurons/metabolism , Peptide Fragments/metabolism , Phosphorylation , Receptors, N-Methyl-D-Aspartate/metabolismABSTRACT
The aim of this study was to study the potential mechanism(s) involved in the antagonist induced upregulation of the N-methyl-d-aspartate receptor (NMDA) NR2B subunit. The results show that chronic treatment of cortical neurons with tyrosine kinase inhibitor (genistein) resulted in downregulation of the NR2B subunit polypeptide levels, while daidzein, an inactive analog of genistein, did not alter the levels of NR2B subunit, implying that tyrosine kinases may be involved in the regulation of the NMDA NR2B subunit content. Chronic treatment of cortical neurons with the NMDA receptor antagonist, (+)-5-methyl-10,11-dihydro-5H-dibenzo[a, d]cycloheptane-5,10-iminemaleate (MK-801) enhanced the membrane associated tyrosine kinase activity and upregulated the NR2B receptor subunit. These results suggest that MK-801 induced upregulation of NMDA (NR2B) receptor subunit might be mediated by tyrosine kinases.
Subject(s)
Neurons/chemistry , Neurons/enzymology , Protein-Tyrosine Kinases/metabolism , Receptors, N-Methyl-D-Aspartate/antagonists & inhibitors , Receptors, N-Methyl-D-Aspartate/metabolism , Animals , Brain Chemistry/drug effects , Brain Chemistry/physiology , Cells, Cultured , Cerebral Cortex/cytology , Dizocilpine Maleate/pharmacology , Enzyme Inhibitors/pharmacology , Estrogens, Non-Steroidal/pharmacology , Excitatory Amino Acid Antagonists/pharmacology , Female , Genistein/pharmacology , Isoflavones/pharmacology , Mice , Mice, Inbred C57BL , Neurons/cytology , Pregnancy , Subcellular Fractions/enzymology , Up-Regulation/drug effects , Up-Regulation/physiologyABSTRACT
We investigated the effect of chronic ethanol administration and its withdrawal on the polypeptide levels of NMDA receptor subunits such as NR1, NR2A, and NR2B in the rat cerebral cortex and hippocampus using Western blot analysis technique. Our results indicate that chronic ethanol treatment upregulates NMDA receptor subunits NR1, NR2A, and NR2B ( approximately 35%). At 48 h of last dose of ethanol administration, the protein content returned to almost control level, thereby demonstrating the reversibility of the changes.
