NMDA receptor activation enhances diazepam binding inhibitor and its mRNA expressions in mouse cerebral cortical neurons

Effects of N-methyl-D-aspartate (NMDA) on diazepam binding inhibitor (DBI) and its mRNA expression in mouse cerebral cortical neurons were examined. A significant increase in DBI mRNA expression was observed 1 day after the e xposure to 0.1 muM NMDA and the maximal expression occurred 2 days after th e exposure, whereas transient exposure to 0.1 muM NMDA for 15 min, 1 and 3 h produced no changes in the expression. Similarly, no changes in the expre ssion were found by the concomitant exposure to NMDA and MK-801, a NMDA rec eptor antagonist, for 72 h subsequent to the incubation with NMDA alone for 3 h. Such NMDA-induced increases in DBI mRNA expression were dose-dependen tly inhibited by MK-801. Moreover, neuronal DBI content significantly incre ased by treatment with NMDA, which was completely abolished by MK-801. Thes e results indicate that continuous activation of NMDA receptors is an essen tial factor for increasing DBI expression in the neurons. (C) 2001 Elsevier Science B.V. All rights reserved.