Which drug class does not directly involve GABA in its mechanism of action?

Buspirone is classified as an anxiolytic that does not directly involve the GABA neurotransmitter in its mechanism of action. Instead, it primarily acts as a serotonin 5-HT1A receptor agonist, which influences serotonin pathways in the brain to exert its anxiolytic effects. This makes it distinct from other drug classes frequently associated with GABA modulation.

In contrast, benzodiazepines, barbiturates, and zolpidem all interact with GABA receptors. Benzodiazepines enhance the effect of GABA at the GABA-A receptor, leading to increased neuronal inhibition. Barbiturates also bind to GABA-A receptors, but they have a different mechanism that can directly activate the receptor even in the absence of GABA. Zolpidem, while chemically different, specifically targets GABA-A receptors with a high affinity for certain subtypes, particularly those that mediate sleep.

Therefore, the significant distinction is that buspirone operates through a different neurotransmitter system rather than modulating GABA activity, making it the correct selection in the context of this question.