Bidirectional transfer between kindling induced by excitatory amino acids and electrical stimulation.

Chemical (C) kindling by means of repeated spaced injections into the amygdala (AM) of a subconvulsive dose of L-glutamate and L-aspartate combined in a molar ratio of 1:3. (Glu/Asp) produced progressive seizure development culminating in generalized convulsion strikingly similar to electrically kindled Stage 5 seizure in rats. These C-kindled AM sites responded readily to electrical stimulation with very rapid development of kindled seizure. When a separate group of rats electrically kindled at the AM were subjected to identical C-kindling at the kindled AM site, a similar positive transfer effect was observed. In addition, 30 days following the last injection, kindled Stage 5 seizure was triggered with a single injection of Glu/Asp, one-half of the dose used for C-kindling. These results suggest that the glutamate and/or aspartate systems participate in the development and persistence of increased seizure susceptibility induced by AM kindling.