Spike Timing-dependent Plasticity Of Neocortical Excitatory Synapses On Inhibitory Interneurons Depends On Target Cell Type

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.