Yohimbine, an alpha-2 adrenergic antagonist, provokes panic attacks in patients with panic disorder by which mechanism?

• A Increasing norepinephrine release via blockade of presynaptic autoreceptors ✓
• B Decreasing norepinephrine release from the locus coeruleus
• C Direct stimulation of the amygdala
• D Blocking serotonin reuptake

Explanation

Yohimbine blocks presynaptic alpha-2 autoreceptors on locus coeruleus neurons, disinhibiting norepinephrine release. This noradrenergic surge provokes panic in panic disorder patients but not in healthy controls, supporting the noradrenergic hyperactivity hypothesis of panic disorder. Sodium lactate and CO2 act through different mechanisms.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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