DL-AP4 is a broad-spectrum glutamatergic antagonist. DL-AP4 (2.5 mM) inhibits electrically stimulated synaptic transmission in rabbit hippocampal slices. It also depresses depolarizations induced by NMDA , L-homocysteate, or kainate in isolated frog spinal cord when used at a concentration of 1 mM. DL-AP4 (0.2 mM) inhibits the accumulation of inositol induced by ibotenate , quisqualate, L-glutamate, and L-aspartate in rat hippocampal slices.