LTP IN THE DENTATE GYRUS IS ASSOCIATED WITH A PERSISTENT NMDA RECEPTOR-DEPENDENT ENHANCEMENT OF SYNAPTOSOMAL GLUTAMATE RELEASE

LTP was induced unilaterally in the dentate gyrus of the anaesthetized rat by tetanic stimulation of the perforant path. Two hours after tet anization synaptosomes were prepared from control and potentiated side s, and the depolarization-induced release of endogenous amino acid neu rotransmitters was compared in the two groups,using 4-aminopyridine, p otassium or veratridine as depolarizing agents. Glutamate release was greater in synaptosomes from potentiated than control tissue with all three depolarizing agents, but the highest release from control synapt osomes and the most significant enhancement of release from ; potentia ted synaptosomes was seen with veratridine. The tetanus-induced enhanc ement of veratridine-induced glutamate release was prevented by pretre atment with MK-801. The results indicate that the induction of LTP in the dentate gyrus is accompanied by a persistent enhancement in the ab ility of synaptosomes to release glutamate in response to a depolarizi ng stimulus.