Subunit selective decrease of AMPA and metabotropic glutamate receptor mRNA expression in rat brain by systemic...

Glutamate mediates its effects in mammals through both ionotropic and metabotropic receptors. Antagonists of ionotropic N-methyl-D-aspartate (NMDA) glutamate receptors elicit neuroprotective and neurotropic effects that have been attributed to Ca2+ block through the membrane ion channel. Nonetheless, molecular and biochemical effects of NMDA receptor antagonism on other glutamate receptor subunits remain poorly understood. We investigated the effects of acute administration of the noncompetitive NMDA receptor antagonist MK-801 on the mRNA expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and metabotropic glutamate receptor (mGluR) subunits to determine the contribution of different glutamate receptors in response to blockade of NMDA receptor channels. In situ hybridization to rat brain sections revealed that AMPAreceptor subunits GluR3 and GluR4, and mGluR3 were modestly but significantly decreased approximately 10-20%, 8 h following 5 mg/kg MK-801 administration. Atime course and dose response study revealed that the effect on mGluR3 was reversed by 24 h and occurred significantly at a dose range from 1 to 5 mg/kg. These results indicate that selected AMPA and mGluR subunit mRNAs respond at the RNA level to the blockade of NMDA receptors.