Long-term potentiation in the avian hippocampus does not require activation of the N-methyl-D-aspartate (NMDA) receptor.

Evoked potentials recorded from slices of pigeon hippocampus were reversibly attenuated by 2 mM kynurenic acid. High frequency stimulation (3 x 200 Hz for 1 sec, with 1 sec intervals) evoked a persistent increase in the evoked potential, lasting in a nondecremental form for at least 2 hr. This increase in the magnitude of the potential was not blocked by antagonists of the NMDA receptor (APV and MK-801). These data suggest that the synaptic facilitation observed in the pigeon hippocampus, which appears to be a form of long-term potentiation, does not depend on the activation of NMDA receptors.