Effect of intrahippocampal quinolinic acid infusion on the amygdala kindling in rat

The effect of intrahippocampal infusion of quinolinic acid (Quin), an endogenous excitatory amino acid, was studied on the amygdala kindling. Quin 120 nmol injected intrahippocampally 2 wk prior to the beginning of amygdala kindling significantly not only produced dorsal hippocampal pyramidal and granule cell loss but also decreased the number of stimuli to trigger the stage 5 seizures of amygdala kindling. In kindled rats, intrahippocampal 20 nmol Quin infusion fully inhibited the stage 5 of amygdala-kindled seizures. The inhibitory effect of Quin was antagonized by dl-2-amino-7-phosphonoheptanoic acid, a selective antagonist of N-methyl-D-aspartate (NMDA) type receptors. The results suggest that NMDA-type receptors in the hippocampus may play a role in the control of the seizure threshold in the amygdala.