Which of the following is a central nervous system depressant?

Which of the following is a central nervous system depressant?

• A. Barbiturates
• B. Cocaine
• C. LSD
• D. Caffeine

Answer: (A)

Barbiturates are central nervous system depressants because they slow brain activity. They accomplish this by enhancing the effects of GABA, the primary inhibitory neurotransmitter in the brain, at the GABA-A receptor. This increases chloride influx into neurons, dampening neuronal firing and producing effects like relaxation, drowsiness, and sleep—effects that become more pronounced at higher doses and can include anesthesia or respiratory depression. The other substances work differently: cocaine is a stimulant that increases dopamine and other monoamines to boost CNS activity; LSD is a psychedelic that alters perception via serotonin systems; caffeine is a stimulant that blocks adenosine receptors to promote wakefulness. Thus barbiturates fit the profile of a CNS depressant.

Barbiturates are central nervous system depressants because they slow brain activity. They accomplish this by enhancing the effects of GABA, the primary inhibitory neurotransmitter in the brain, at the GABA-A receptor. This increases chloride influx into neurons, dampening neuronal firing and producing effects like relaxation, drowsiness, and sleep—effects that become more pronounced at higher doses and can include anesthesia or respiratory depression. The other substances work differently: cocaine is a stimulant that increases dopamine and other monoamines to boost CNS activity; LSD is a psychedelic that alters perception via serotonin systems; caffeine is a stimulant that blocks adenosine receptors to promote wakefulness. Thus barbiturates fit the profile of a CNS depressant.