An antagonist is a molecule that ...

• A. Enhances neurotransmitter release
• B. Blocks action from the neuron
• C. Mimics neurotransmitter
• D. Causes neurotransmitter synthesis

Answer: (B)

An antagonist blocks the action of a neurotransmitter by binding to its receptor without activating it, preventing the neurotransmitter from triggering a response. This is why it reduces signaling at the synapse. An agonist, in contrast, would mimic the neurotransmitter and activate the receptor. Also, increasing neurotransmitter release or raising its synthesis would boost signaling rather than block it. Hence, blocking receptor activation best describes an antagonist.