Final answer:
AMPA receptors open in response to glutamate, allowing Na+ influx while typically being impermeable to Ca2+ due to the GluA2 subunit. Calcium-permeable AMPA receptors without edited GluA2 are implicated in neurodegeneration. NMDA receptors work in tandem with AMPA receptors, contributing to synaptic plasticity by controlling Ca2+ influx after Mg2+ removal.
Step-by-step explanation:
AMPA receptors open in response to the neurotransmitter glutamate. These receptors allow a rapid influx of sodium ions (Na+) into the postsynaptic neuron, which changes the cell's electrical potential and can contribute to synaptic signaling. Most AMPA receptors contain a GluA2 subunit, which is edited to include an arginine residue, rendering the channel impermeable to calcium ions (Ca2+). This selective ion permeability is critical for the receptor's role in synaptic plasticity and for avoiding excitotoxicity that can occur if too much calcium enters the cell. However, AMPA receptors lacking the edited GluA2 subunit can be permeable to calcium, which is associated with cell damage in neurodegenerative disorders like ALS. Thus, the trafficking of AMPA receptors with or without GluA2 is a process of immense interest within the context of neurological health and dysfunction.
Another receptor, the NMDA receptor, has a synergistic role with AMPA receptors in synaptic plasticity. NMDA receptors become fully active when depolarization of the postsynaptic cell removes an inhibitory magnesium ion (Mg2+ from the receptor, allowing calcium to enter the cell and initiate further signaling processes important for learning and memory.