Previous NMDA activation is not required for the increased ease in inducing a long-lasting LTP.

<p>The bars represent the fEPSP slopes obtained 2 h after LTP induction by a single train (100 Hz, 1 s) when dissection and recovery occurred during perfusion of varied ACSF solutions whereas normal ACSF was applied during LTP induction and LTP maintenance. Dissection and recovery of slices were carried out in ACSF either of normal composition (n = 3), without Ca⁺⁺ (n = 2), with 2.6 mM Mg⁺⁺ (n = 2) or added with 50 µM APV, an NMDA receptor inhibitor (n = 3).