**Core Concept**
GABA (Gamma-Aminobutyric Acid) is an inhibitory neurotransmitter that plays a crucial role in regulating neuronal excitability throughout the nervous system. It acts through specific receptors to produce its effects, including sedation, relaxation, and reduced anxiety.

**Why the Correct Answer is Right**
The correct answer is the one that does not act through GABA receptors. GABA's primary mechanism involves binding to GABA_A receptors, which are ligand-gated chloride channels that allow chloride ions to enter the neuron, hyperpolarizing it and reducing excitability. Other neurotransmitters and drugs that act through GABA receptors include benzodiazepines, barbiturates, and certain anticonvulsants.

**Why Each Wrong Option is Incorrect**
**Option A:**
This option is incorrect because it is a GABA_A receptor agonist, meaning it directly activates GABA_A receptors to produce anxiolytic and sedative effects.

**Option B:**
This option is incorrect because it is a GABA_A receptor antagonist, meaning it blocks the action of GABA at GABA_A receptors, leading to increased neuronal excitability and potentially convulsive effects.

**Option C:**
This option is incorrect because it is a GABA_A receptor agonist, similar to benzodiazepines, and acts through GABA_A receptors to produce anxiolytic and sedative effects.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that GABA's inhibitory effects can be either beneficial (e.g., reducing anxiety) or detrimental (e.g., leading to respiratory depression). Understanding the mechanisms of GABA and its interactions with other neurotransmitters is crucial for managing various neurological and psychiatric conditions.

**Correct Answer:** D.