**Core Concept**
Mirtazapine is a unique antidepressant that acts as an antagonist at specific receptors in the central nervous system, which differentiates it from other antidepressants. This action is primarily targeted at central presynaptic α2-adrenergic receptors and serotonin 5-HT2 and 5-HT3 receptors.

**Why the Correct Answer is Right**
Mirtazapine's mechanism of action involves the antagonism of central presynaptic α2-adrenergic receptors, which leads to an increase in the release of norepinephrine and serotonin. This action also involves the antagonism of serotonin 5-HT2 and 5-HT3 receptors, which contributes to its anxiolytic and antidepressant effects. By blocking these receptors, mirtazapine enhances the activity of norepinephrine and serotonin in the synaptic cleft, ultimately leading to improved mood and reduced anxiety.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because mirtazapine does not primarily act as a dopamine receptor antagonist. While it may have some effect on dopamine levels, its primary mechanism involves the antagonism of α2-adrenergic receptors and serotonin receptors.
**Option B:** This option is incorrect because mirtazapine does not primarily act as a histamine receptor antagonist. While it may have some antihistaminic effects, this is not its primary mechanism of action.
**Option C:** This option is incorrect because mirtazapine does not primarily act as a GABA receptor antagonist. While it may have some effect on GABA levels, its primary mechanism involves the antagonism of α2-adrenergic receptors and serotonin receptors.

**Clinical Pearl / High-Yield Fact**
Mirtazapine's unique mechanism of action, involving the antagonism of central presynaptic α2-adrenergic receptors and serotonin 5-HT2 and 5-HT3 receptors, sets it apart from other antidepressants and makes it a useful option for patients with treatment-resistant depression or anxiety disorders.

**Correct Answer:** C. serotonin 5-HT2 and 5-HT3 receptors