**Core Concept**
Nitrates are a class of medications used to treat angina pectoris by reducing the oxygen demand of the myocardium. They exert their effects by releasing nitric oxide (NO), a potent vasodilator that relaxes vascular smooth muscle and increases blood flow to the coronary arteries.

**Why the Correct Answer is Right**
Nitrates work by converting to nitric oxide (NO) in the cytosol of vascular smooth muscle cells. NO then activates soluble guanylyl cyclase (sGC), leading to an increase in cyclic guanosine monophosphate (cGMP) levels. Elevated cGMP levels cause smooth muscle relaxation, resulting in vasodilation of peripheral and coronary blood vessels. This reduction in vascular resistance decreases the afterload on the heart, thereby reducing the oxygen demand of the myocardium.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because nitrates do not act by inhibiting the reuptake of catecholamines.
**Option B:** This option is incorrect because nitrates do not primarily act by increasing the contractility of the heart.
**Option C:** This option is incorrect because nitrates do not primarily act by reducing the heart rate.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that nitrates are contraindicated in patients with hypotension, as they can further decrease blood pressure, potentially leading to organ hypoperfusion.

**Correct Answer: C.**