Which neurotransmitter is central to NMDA receptor-dependent long-term potentiation, a cellular basis of learning?

• A. Glutamate
• B. Dopamine
• C. GABA
• D. Serotonin

Answer: (A)

Glutamate is the key neurotransmitter driving NMDA receptor-dependent long-term potentiation. This form of LTP strengthens a synapse after repeated activity, and at the core of it are NMDA receptors that respond to glutamate. When glutamate binds and the postsynaptic neuron is sufficiently depolarized, the Mg2+ block of NMDA receptors is removed, allowing calcium to surge into the cell. This calcium influx triggers signaling cascades that increase the strength of the synapse, such as more AMPA receptors being inserted and changes in gene expression, solidifying the learning-related changes. Dopamine, GABA, and serotonin can influence learning and plasticity in various circuits, but they are not the primary transmitter that activates NMDA receptor-dependent LTP; GABA is inhibitory, and the others modulate but do not directly initiate this specific mechanism.