Spiking activity can induce persistent modification of excitatory synapses in cortical circuits. Here we report that such modification exhibits target cell-dependent properties. In layer 2/3 of the somatosensory cortex, the pyramical cell (PC) forms divergent synapses on fast spiking (FS) and low-threshold spiking (LTS) interneurons. Correlated pre- and postsynaptic spiking induced long-term potentiation (LTP) or depression (LTD) at PC-LTS synapses, depending on the timing of pre/post spiking. However, regardless the timing and frequency of spiking, correlated activity induced only LTD at PC-FS synapses, which have a much lower level of N-methyl-D-aspartate subtype of glutamate receptors (NMDARs) than that of PC-LTS synapses. Furthermore, activation of NMDARs was required for LTP at PC-LTS synapses, whereas activation of metabotropic glutamate receptors (mGluRs) rather than NMDARs was required for LTD of both PC-LTS and PC-FS synapses. This target cell-specific synaptic plasticity allows for differential processing and storage of information in cortical local circuits.
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