Alpha2 Adrenergic Receptor Agonist 1

Question

Vignette:

A 45-year-old woman with a history of chronic obstructive pulmonary disease (COPD) presents to the emergency room with worsening shortness of breath and productive cough. After initial assessment, she is diagnosed with an acute COPD exacerbation. The physician decides to start her on a medication that selectively stimulates β2-adrenergic receptors. Which of the following is the most likely mechanism of action of this drug?

Choices

A. Increase in intracellular cyclic AMP levels

B. Inhibition of cyclic AMP production

C. Decrease in intracellular calcium levels

D. Promotion of GABA activity

E. Inhibition of norepinephrine reuptake

Answer

A. Increase in intracellular cyclic AMP levels

Explanation

β2-Adrenergic agonists, such as albuterol, are commonly used to treat acute exacerbations of COPD and asthma. These drugs work by binding to β2-adrenergic receptors on bronchial smooth muscle cells, leading to activation of adenylate cyclase and increased production of cyclic AMP. The increase in cyclic AMP levels leads to relaxation of bronchial smooth muscle and bronchodilation, which helps to relieve the symptoms of COPD and asthma. Thus, the correct answer is A. Increase in intracellular cyclic AMP levels.

Choice B is incorrect, as β2-adrenergic agonists actually stimulate, not inhibit, the production of cyclic AMP. Choice C is incorrect because while some medications can decrease intracellular calcium levels to cause smooth muscle relaxation, this is not the mechanism of β2-adrenergic agonists. Choice D and E are incorrect as they describe mechanisms of action for other types of drugs - benzodiazepines and tricyclic antidepressants, respectively - but not β2-adrenergic agonists.