THE GLUTAMATE INHIBITION OF CARBACHOL-STIMULATED INOSITOL PHOSPHATE PRODUCTION IN RAT CORTICAL-CELLS IS MEDIATED THROUGH AN IONOTROPIC NMDARECEPTOR

Carbachol (0.1 mM) stimulated accumulation of inositol monophosphate ( IP1)(3-4 fold of basal, P < 0.001) in fetal rat cortical cells is atte nuated by glutamate (at 0.1 mM, 40-70% of carbachol alone, P < 0.001). This inhibition by glutamate was reduced by 2-amino-5-phosphonopentan oic acid (AP5), but not by gamma-D-SCPnic acid (GAMS) or 2-amino-3-pho sphonopropionic acid (AP3). The metabotropic receptor agonist (LS,3R)- 1-aminocyclopentane-1-3-dicarboxylic acid [(LS,3R)-ACPD] (up to 0.1 mM ) had no effect upon carbachol stimulated IP1. Staurosporine and quina crine were unable to prevent the inhibition of carbachol stimulated IP 1 by glutamate. These data suggest that the inhibition of carbachol-st imulated IP1, by glutamate in rat cortical cells is mediated through a n NMDA ionotropic receptor.