Suppression of ictal-like activity by kynurenic acid does not correlate with its efficacy as an NMDA receptor antagonist.

The involvement of excitatory amino acid (EAA) receptors in ictal-like activity was investigated using hippocampal slices from immature rats. Bath application of kynurenic acid (KYN) suppressed penicillin-induced synchronized afterdischarges. An identical concentration of D(-)2-amino-5-phosphonovaleric acid (D(-)AP5) spared the afterdischarges. Intracellular recordings confirmed D(-)AP5 to be the more potent N-methyl-D-aspartate antagonist. KYN's suppression of afterdischarges could not be clearly attributed to blockade of either kainate or quisqualate receptors. Thus, a novel kynurenate-preferring EAA receptor may play an important role in seizure generation in immature hippocampus.