Glutamate receptor antagonists do not block TA-induced SC depotentiation.

(A) The graph shows the time course of change in SC EPSPs following a single 100 Hz x 1 sec HFS delivered to the SC pathway (arrow). After establishing SC LTP, 1 Hz LFS of the TA (perforant path) inputs to CA1 (PLFS, hatched bar) reversed LTP. (B) Following stable SC LTP induction 30 μM CNQX (black bar) was administered and inhibited SC EPSPs completely. CNQX did not prevent LTP-D by PLFS (white circles) and had no effect on LTP by itself (black circles). (C) A combination of glutamate receptor antagonists (30 μM CNQX, 100 μM APV and 500 μM MCPG) also failed to prevent PLFS-induced LTP-D. Traces to the right of the graphs show representative field EPSPs at the times indicated (black lines) with baseline EPSPs shown as dashed traces. Calibration: 1 mV, 5 ms.