Effects of NMDA antagonists on seizure thresholds induced by intrahippocampal microdialysis of picrotoxin in freely moving rats.

The role of N-methyl-D-aspartate (NMDA) receptors on individual variations in animal seizure threshold induced by picrotoxin microperfusion in the hippocampus of freely moving rats was analyzed by testing the effects of NMDA receptor antagonists 2-amino 5-phosphonovalerate (AP-5) and dizocilpine (MK-801) on individual seizure thresholds. We found a correlation between the increased threshold levels induced by AP-5 and control seizure levels of each individual animal. However, no correlation was found with the increased threshold level induced by MK-801. These data suggest that the individual variations in seizure threshold in different animals reflect dynamic processes of NMDA mediated activity and emphasizes the value of whole-animal models to analyze NMDA receptor functions.