A, synaptic efficacy changes induced by STDP protocols within −40 < Δt < +60 ms were plotted in control (n = 20) and AP5 (50 μm) treatment (n = 10). B, long-term synaptic efficacy changes induced by post-pre protocols for −40 < Δt < 0 ms, in control (n = 10) (open bar) and in AP5 treatment (50 μm) (n = 6) (filled bar). In control, post-pre protocols induced significant LTD (−39.5 ± 8.3%, n = 10) and in AP5 treatment no more LTD was induced and an absence of long-term plasticity was observed (92.5 ± 6.5%, n = 6). C, long-term synaptic efficacy changes induced by pre-post protocols for 0 < Δt < +40 ms in control (n = 10) (open bar) and in AP5 treatment (n = 4) (filled bar). In control, pre-post protocols induced significant LTP (+42.2 ± 11.6%, n = 9) and in AP5 treatment no more LTP was observed but an absence of long-term plasticity (96.3 ± 11.9%, n = 4). AP5 abolished both LTD and LTP induced, respectively, by post-pre and pre-post protocols in control. This indicates that in GABAergic interneuron LTD and LTP are NMDA receptor-activation dependent.