Which statement correctly describes the roles of NMDA and AMPA receptors in synaptic plasticity and the Mg2+ block at rest?

• A. NMDA receptors mediate fast excitatory transmission; AMPA requires depolarization to relieve Mg2+ block and trigger plasticity.
• B. AMPA mediates fast excitatory transmission; NMDA requires co-agonists and depolarization to relieve Mg2+ block; Ca2+ influx through NMDA triggers signaling for plasticity.
• C. AMPA receptors relieve Mg2+ block and provide calcium signaling independent of depolarization.
• D. Ca2+ influx through AMPA receptors triggers plasticity by activating signaling cascades.

Answer: (B)