High concentrations of glycine induce long-lasting changes in synaptic efficacy in rat hippocampal slices.

Brief perfusion of adult rat hippocampal slices with high concentrations of glycine results in a slowly developing, long-lasting increase in synaptic responses in field CA1. Two observations indicated that the effect requires the activation of NMDA receptors by glycine. First, the glycine-induced potentiation is reduced by ketamine, an NMDA receptor channel blocker. Second, glycine potentiates the NMDA receptor-mediated epileptiform activity recorded in the presence of low magnesium concentration and picrotoxin. In slices prepared from rat pups (5-8 postnatal day), perfusion with glycine results in a slowly developing, long-lasting depression of EPSP amplitude. These results provide a new way of producing potentiation of synaptic efficacy and suggest new properties of NMDA receptors.