Final answer:
Blocking NMDA receptors in the hippocampus after LTP or training, inhibiting CamKII before LTP or training, and blocking protein synthesis during LTP induction and training have been shown to prevent long-term LTP or learning/memory.
Step-by-step explanation:
To prevent both long-term LTP or learning/memory, blocking NMDA receptors in the hippocampus after LTP or training (option 1), inhibiting CamKII before LTP or training (option 2), and blocking protein synthesis during LTP induction and training (option 3) have all been shown to be effective. On the other hand, inhibiting protein kinase M zeta a day after LTP induction or training (option 4) and blocking NMDA receptors in the hippocampus before LTP or training (option 5) have not been shown to prevent long-term LTP or learning/memory.