Ferrous iron modulates quinolinate-mediated [H-3]MK-801 binding to rat brain synaptic membranes in the presence of glycine and spermidine

Quinolinic acid (QUIN) displaced binding of agonist and antagonist ligands for the N-methyl-D-aspartate (NMDA) receptor in rat brain synaptic membrane s. Both QUIN and glutamic acid (GLU) potentiated binding of [H-3]dizocilpin e (MK-801) in the presence of glycine (GLY) alone, whereas the potentiation by QUIN was in a bell-shaped fashion in contrast to that by GLU. However, further addition of spermidine (SPD) induced bell-shaped potentiation by GL U as well as QUIN. The potentiation by QUIN was markedly deteriorated by th e further addition of FeCl2 irrespective of the presence of GLY and SPD add ed. These results suggest that QUIN may potentiate [H-3]MK-801 binding to t he open NMDA channel in rat brain synaptic membranes through a mechanism di fferent from that underlying the potentiation by GLU. (C) 1999 Elsevier Sci ence Ireland Ltd. All rights reserved.