题目

A 66-year-old man with chronic hypertension is treated with prazosin by his physician. The treatment successfully decreases his blood pressure to within the normal range. What is the mechanism of the drug's action?A. Stimulation of muscarinic receptors in the SA nodeB. Inhibition of alpha_1 receptors on vascular smooth muscleC. Stimulation of beta_1 receptors in ventricular muscleD. Stimulation of nicotinic receptors in the SA node

A 66-year-old man with chronic hypertension is treated with prazosin by his physician. The treatment successfully decreases his blood pressure to within the normal range. What is the mechanism of the drug's action?

A. Stimulation of muscarinic receptors in the SA node

B. Inhibition of $\alpha_1$ receptors on vascular smooth muscle

C. Stimulation of $\beta_1$ receptors in ventricular muscle

D. Stimulation of nicotinic receptors in the SA node

题目解答

答案

B. Inhibition of $\alpha_1$ receptors on vascular smooth muscle

解析

本题考查抗高血压药物的作用机制，核心在于识别哌唑嗪（Prazosin）的药理作用特点。
关键点：

  1. 哌唑嗪属于选择性α₁受体阻断剂，通过阻断血管平滑肌上的α₁受体，抑制血管收缩，降低外周阻力。
  2. 需区分其他选项中涉及的受体类型（如β₁受体、胆碱能受体）及其生理作用，排除干扰项。

药物作用机制分析

  1. 哌唑嗪的分类
    哌唑嗪是第二代α₁受体阻断剂，主要作用于血管平滑肌，而非心脏或其他组织。

  2. α₁受体的功能
    α₁受体激活时（如交感神经释放去甲肾上腺素），会引起血管平滑肌收缩，导致外周血管阻力增加、血压升高。

  3. 哌唑嗪的作用
    通过竞争性阻断α₁受体，哌唑嗪抑制血管收缩，使血管舒张，降低外周阻力，从而有效降低血压。

选项逐一解析

  • A. 刺激毒蕈碱受体
    毒蕈碱受体（M受体）激活会减慢心率、降低心肌收缩力，但与哌唑嗪无关。
  • B. 抑制α₁受体
    正确。直接对应哌唑嗪的核心作用机制。
  • C. 刺激β₁受体
    β₁受体激活会增强心肌收缩，升高血压，与降压效果矛盾。
  • D. 刺激烟碱受体
    烟碱受体（N受体）主要分布在神经节，与血管调节无关。