**Core Concept**
Nitrates are a class of vasodilatory drugs that act by releasing nitric oxide (NO), leading to smooth muscle relaxation and vasodilation. This results in a decrease in blood pressure, reduced myocardial oxygen demand, and increased blood flow to ischemic myocardium.

**Why the Correct Answer is Right**
The correct mechanism of action of nitrates involves the conversion of nitroglycerin to nitric oxide (NO) by the enzyme aldehyde dehydrogenase. NO then activates soluble guanylyl cyclase, which increases cyclic guanosine monophosphate (cGMP) levels, leading to smooth muscle relaxation and vasodilation. Nitrates are particularly useful in the treatment of angina pectoris, as they reduce myocardial oxygen demand and increase blood flow to ischemic myocardium.

**Why Each Wrong Option is Incorrect**
**Option A:** This statement is incorrect because nitrates do not directly stimulate the release of acetylcholine. Instead, they act through the release of nitric oxide, which then activates guanylyl cyclase.
**Option B:** This statement is incorrect because nitrates do not primarily act by inhibiting the reuptake of norepinephrine. Their primary mechanism of action is through the release of nitric oxide, which then activates guanylyl cyclase.
**Option C:** This statement is incorrect because nitrates do not directly increase the contractility of the heart. Instead, they reduce myocardial oxygen demand through vasodilation and reduced blood pressure.

**Clinical Pearl / High-Yield Fact**
Nitrates can cause tolerance with chronic use due to the upregulation of aldehyde dehydrogenase, the enzyme responsible for converting nitroglycerin to nitric oxide. This can be avoided by using intermittent dosing or alternative vasodilators.

**Correct Answer: C.