Question

A patient with chronic hypertension is treated with prazosin by his physician. The treatment successfully decreases the patient's blood pressure to within the normal range. What is the mechanism of the drug's action?

(A) Inhibition of 13 1 receptors in the sinoatrial
(SA) node
(B) Inhibition of P2 receptors in the SA node
(C) Stimulation of muscarinic receptors in the
SA node
(D) Stimulation of nicotinic receptors in the
SA node
(E) Inhibition of 131 receptors in ventricular
muscle
(F) Stimulation of 13, receptors in ventricular
muscle
(G) Inhibition of al receptors in ventricular
muscle

Answer 1

Prazosin lowers blood pressure by inhibiting α1 receptors on vascular smooth muscle cells, causing vasodilation and reducing vascular resistance.

Step-by-step explanation:

The mechanism of action for prazosin, a medication used to treat chronic hypertension, is through the inhibition of α1 receptors located on smooth muscle cells in blood vessels. Prazosin is an α-blocker, and by inhibiting these receptors, it prevents the action of endogenous catecholamines, like norepinephrine, which normally cause blood vessels to constrict. As a result, the blood vessels dilate, reducing vascular resistance and thereby lowering the blood pressure. This vasodilatory effect brings the blood pressure within a normal range for patients with hypertension. Prazosin does not act on the sinoatrial (SA) node, beta receptors, or muscarinic and nicotinic receptors in the heart as might be suggested by the alternative options provided in the question.