How do selective alpha-1 blockers like prazosin work?

Selective alpha-1 blockers like prazosin function by competitively inhibiting alpha-1 adrenergic receptors. These receptors are primarily located on smooth muscle cells in blood vessels. When alpha-1 receptors are activated by catecholamines such as norepinephrine, they cause vasoconstriction, leading to increased blood pressure.

By blocking these receptors, prazosin induces vasodilation, which results in lowered peripheral vascular resistance and, consequently, reduced blood pressure. This mechanism makes prazosin effective in treating conditions like hypertension and benign prostatic hyperplasia, where relaxation of smooth muscle can alleviate symptoms.

The other options do not accurately describe the mechanism of action for selective alpha-1 blockers. For instance, inhibiting calcium channels in the heart is more characteristic of calcium channel blockers, while decreasing LDL receptor activity relates to statins or other lipid-modifying agents. Similarly, inhibiting the synthesis of serotonin is associated with different classes of medications like certain antidepressants and is not connected to alpha-1 adrenergic receptor blocking.