**Core Concept**
Selective alpha-2 antagonists are a class of medications that block the action of alpha-2 adrenergic receptors, which are involved in various physiological processes such as vasoconstriction, sedation, and inhibition of neurotransmitter release. By selectively blocking alpha-2 receptors, these agents can increase the release of norepinephrine and other neurotransmitters, leading to increased alertness and wakefulness.

**Why the Correct Answer is Right**
Methoxamine is a selective alpha-1 agonist, not an antagonist and the question asks for an antagonist. However, the correct answer is actually **Yohimbine**. Yohimbine is a selective alpha-2 antagonist that blocks the pre-synaptic alpha-2 receptors, leading to an increase in the release of norepinephrine and other neurotransmitters. This results in increased alertness, wakefulness, and arousal. Yohimbine also has been used to treat erectile dysfunction and as an adjunct in the treatment of depression.

**Why Each Wrong Option is Incorrect**
* **Option A:** Yohimbine is not a selective alpha-2 antagonist, but the correct answer is indeed yohimbine. However, the distractor could be something like **Methoxamine**, which is a selective alpha-1 agonist, not an antagonist.
* **Option B:** This option is missing.
* **Option C:** This option is missing.
* **Option D:** This option is missing.

**Clinical Pearl / High-Yield Fact**
Selective alpha-2 antagonists like yohimbine can increase the risk of hypertensive crises in patients with pheochromocytoma or other conditions where alpha-2 receptors are overactive.

**Correct Answer: . Yohimbine**