Chemical substances that mimic or enhance the effects of a neurotransmitter on receptor sites, increasing or decreasing the activity of that cell are called what?

• A. Antagonists
• B. Neuromodulators
• C. Neurotransmitters
• D. Agonists

Answer: (D)

Agonists are substances that bind to receptor sites and activate them, mimicking the action of a neurotransmitter. By turning receptors on, they increase the post-synaptic response and boost the cell’s activity. Some agonists closely resemble the natural transmitter, producing similar effects, while others stabilize the receptor in its active state to enhance signaling. This makes them the best fit for describing chemical substances that imitate or amplify neurotransmitter effects. Antagonists block receptors and reduce activity, neuromodulators alter the strength or timing of signaling without directly activating receptors, and neurotransmitters are the brain’s own chemical messengers.