Which substance is classified as a depressant?

Which substance is classified as a depressant?

• A. Alcohol
• B. Caffeine
• C. LSD
• D. Nicotine

Answer: (A)

Depressants slow brain and body activity by boosting inhibitory signaling in the nervous system. Alcohol fits this pattern by enhancing GABA_A receptor activity, which makes neurons less likely to fire. That increased inhibition leads to slower thinking, slowed reflexes, and impaired coordination, classic signs of a depressant effect. It also dampens excitatory glutamate signaling, contributing to memory problems and sedation at higher doses. Caffeine, in contrast, is a stimulant that blocks adenosine receptors, increasing alertness and arousal. LSD is a hallucinogen that primarily alters serotonin signaling to change perception, not to depress CNS activity. Nicotine acts as a stimulant via nicotinic acetylcholine receptors, boosting alertness and dopamine release. Therefore, the substance classified as a depressant is alcohol.

Depressants slow brain and body activity by boosting inhibitory signaling in the nervous system. Alcohol fits this pattern by enhancing GABA_A receptor activity, which makes neurons less likely to fire. That increased inhibition leads to slower thinking, slowed reflexes, and impaired coordination, classic signs of a depressant effect. It also dampens excitatory glutamate signaling, contributing to memory problems and sedation at higher doses.

Caffeine, in contrast, is a stimulant that blocks adenosine receptors, increasing alertness and arousal. LSD is a hallucinogen that primarily alters serotonin signaling to change perception, not to depress CNS activity. Nicotine acts as a stimulant via nicotinic acetylcholine receptors, boosting alertness and dopamine release. Therefore, the substance classified as a depressant is alcohol.