Rapid redistribution of glutamate receptors contributes to long-term depression in hippocampal cultures

Synaptic strength can be altered by a variety of pre- or postsynaptic modif ications. Here we test the hypothesis that long-term depression (LTD) invol ves a decrease in the number of glutamate receptors that are clustered at i ndividual synapses in primary cultures of hippocampal neurons. Similar to a prominent form of LTD observed in hippocampal slices, LTD in hippocampal c ultures required NMDA receptor activation and was accompanied by a decrease in the amplitude and frequency of miniature excitatory postsynaptic curren ts. Immunocytochemical analysis revealed that induction of LTD caused a con current decrease in the number of AMPA receptors clustered at synapses but had no effect on synaptic NMDA receptor clusters. These results suggest tha t a subtype-specific redistribution of synaptic glutamate receptors contrib utes to NMDA receptor-dependent LTD.