What happens when glutamate binds to NMDA receptors during neuronal activation?

When glutamate binds to NMDA receptors during neuronal activation, it initiates a series of events critical for synaptic plasticity and memory formation. NMDA receptors are unique among glutamate receptors in that they are voltage- and ligand-gated, meaning they require both the binding of glutamate (the ligand) and depolarization of the postsynaptic membrane to function properly.

Upon binding of glutamate to the NMDA receptor, the receptor undergoes a conformational change that results in the removal of magnesium ions, which typically block the channel at resting membrane potential. Once this magnesium block is removed—often due to the depolarization of the neuron—calcium ions can enter the cell through the open NMDA channel. The influx of calcium is crucial, as it acts as a second messenger within the neuron, leading to various signaling cascades that contribute to synaptic strengthening, a phenomenon known as long-term potentiation (LTP).

This mechanism is fundamental to understanding how activity in neural pathways can lead to changes in synaptic strength, which is a key aspect of learning and memory. Therefore, the correct answer highlights the critical role that NMDA receptors play in excitatory neurotransmission and neuronal plasticity by allowing calcium entry following the ejection