What is a primary use of barbiturates?

Barbiturates are primarily recognized for their use as sedatives. These central nervous system depressants work by enhancing the effect of the neurotransmitter gamma-aminobutyric acid (GABA) in the brain, which leads to a calming effect on the body and mind. Due to their sedative properties, barbiturates have historically been prescribed for anxiety, insomnia, and seizure disorders.

The other options do not accurately reflect the primary use of barbiturates. For instance, increasing alertness and stimulating brain activity are functions more associated with stimulants rather than depressants. Similarly, enhancing appetite is not a recognized use of barbiturates, as sedatives generally have a calming effect rather than stimulating appetite. Therefore, option B correctly identifies the primary function of barbiturates in the context of their pharmacological effects.