The Expression of NMDA Receptor Subunits in Cerebral Cortex and Hippocampus is Differentially Increased by Administration of Endobain E, a Na+, K+-ATPase Inhibitor

Previous studies showed that endobain E, an endogenous Na + , K + -ATPase inhibitor, decreases dizocilpine binding to NMDA receptor in isolated membranes. The effect of endobain E on expression of NMDA receptor subunits in membranes of rat cerebral cortex and hippocampus was analyzed by Western blot. Two days after administration of 10 μl endobain E (1 μl = 29 mg fresh tissue) NR1 subunit expression enhanced 5-fold and 2.5-fold in cerebral cortex and hippocampus, respectively. NR2A subunit expression increased 2-fold in cerebral cortex and 1.5-fold in hippocampus. The level of NR2B subunit raised 3-fold in cerebral cortex but remained unaltered in hippocampus. NR2C subunit expression was unaffected in either area. NR2D subunit enhanced 1.6 and 2.1-fold for cerebral cortex and hippocampus, respectively. Results indicate that endogenous Na + , K + -ATPase inhibitor endobain E differentially modifies the expression of NMDA receptor subunits.