National Certified Addiction Counselor, Level 2 (NCAC II) Practice Exam Exam

Which psychoactive substance is known as an agonist?

1. A substance that inhibits neuronal activity

2. A psychoactive substance that enhances neurotransmitter effects

3. A drug that binds and mimics neurotransmitters

4. A medication that blocks neurotransmitter activity

The correct answer is: A drug that binds and mimics neurotransmitters

The correct answer highlights the characteristic of a drug that interacts directly with neurotransmitter systems in the brain. Specifically, an agonist is a substance that binds to a receptor and activates it, mimicking the action of a naturally occurring neurotransmitter. By doing this, agonists can increase the likelihood of a neuronal response, thereby enhancing the signaling that occurs. For instance, opioids are classic examples of agonists because they bind to opioid receptors and produce effects similar to endogenous opioids, such as endorphins. This interaction can lead to increased feelings of pleasure, pain relief, and other physiological responses important in both the therapeutic and addictive contexts of substance use. The rationale for the other options revolves around different mechanisms of action. A substance that inhibits neuronal activity describes an antagonist rather than an agonist, as it would block or reduce neurotransmitter effects. Similarly, while enhancing neurotransmitter effects is somewhat aligned with agonist activity, it does not capture the essence of how they specifically function at the receptor level. Lastly, a medication that blocks neurotransmitter activity clearly refers to antagonistic action, which opposes the role of an agonist.