Antagonism of monosynaptic excitations in the mouse olfactory cortex slice by 6,7-dinitroquinoxaline-2,3-dione

Abstract

The effects of 6,7-dinitroquinoxaline-2,3-dione (DNQX) have been tested in slices of olfactory cortex of the mouse against responses evoked by N- methyl- d-aspartate , kainate and quisqualate and on the surface field potentials evoked on electrical stimulation of the lateral olfactory tract. At a concentration of 5 μM, DNQX competitively antagonized responses evoked by kainate and quisqualate, with only a small reduction in the responses to N- methyl- d-aspartate . In contrast, dl-(±)-2-amino-5-phosphonopentanoic acid (APP, 50 μM) selectively antagonized depolarizations to N- methyl- d-aspartate . The amplitude of the field potential known as the N-wave was reduced by DNQX in a concentration- dependent reversible manner (IC 50 = 2.92 ± 0.33 μM; mean ± SE mean, n = 4). dl-(±)-2-Amino-5-phosphonopentanoic acid (50 μM) did not significantly affect this action of DNQX. It is concluded that DNQX inhibits monosynaptic excitations in the olfactory cortex by selectively blocking kainate and/or quisqualate receptors, although it is unclear whether the receptors are located at pre- and/or postsynaptic sites.