Ketamine blocks the induction of LTP at the lateral entorhinal cortex-dentate gyrus synapses

In many regions NMDA receptor activation is required for the synaptic induction of long-term potentiation (LTP). This role for NMDA receptors is controversial at the synapses formed between the cells of the lateral entorhinal cortex (LEC) and the dentate gyrus (DG). Using anesthetized rats, the present study shows that ketamine reversibly blocks the induction of LTP at the LEC-DG synapses, thus favoring a role for NMDA receptors in the induction of LTP there. Ketamine also reversibly blocks the induction of the small translaminar depression of the medial EC response or of the LEC response by conditioning the other system while the test system is inactive.