Aims: Tolerance to ethanol-induced inhibition of N-methyl-D-aspartate receptors (NMDARs) is thought to underlie the acute adaptive mechanisms against ethanol. To explore these compensatory upregulating mechanisms of NMDARs, we investigated the expression and phosphorylation of NMDAR subunits in vivo following an acute ethanol treatment.
Methods: Male Sprague-Dawley rats were given 4 g/kg ethanol, and the phospho-S896-NR1, NR2A and NR2B subunits of NMDAR were immunoblotted from the cerebral cortex and hippocampus. We also examined the mRNAs and ubiquitinated forms of the NR2A and NR2B subunits.
Results: Acute ethanol treatment increased phospho-S896-NR1 at 30 min in the cerebral cortex and hippocampus, and the increase was maintained until 2 h in the hippocampus. Ethanol increased total NR2A and NR2B expression at 30 min in the cortex and hippocampus, and the NR2A increase was maintained until 2 h in the hippocampus. The increased expression of the NR2A and NR2B subunits was not associated with statistically significant alterations in mRNA expression or protein ubiquitination.
Conclusion: Acute ethanol treatment increased NR1 subunit phosphorylation and NR2A and NR2B subunit expression in the cerebral cortex and hippocampus of rats. These effects of ethanol on the NMDAR subunits may underlie the mechanisms that compensate for ethanol-induced inhibition of NMDARs. However, the regulation of NR2A and NR2B in this paradigm is not dependent on transcriptional changes.