Which of the following is an action of beta-blockers?

Beta-blockers, also known as beta-adrenergic antagonists, primarily function by blocking the effects of epinephrine (adrenaline) and other stress hormones on beta-adrenergic receptors in the body, particularly in the heart. One of the most significant actions of beta-blockers is lowering the heart rate, which they achieve by reducing the heart's workload and oxygen demand. By inhibiting the stimulation of beta-1 receptors in the heart, beta-blockers decrease both the rate and force of heart contractions, leading to a reduction in heart rate.

This action makes beta-blockers particularly useful in conditions such as hypertension, heart failure, and certain types of arrhythmias, where managing heart rate and overall cardiac output is crucial. Additionally, lowering the heart rate can help alleviate symptoms of anxiety and reduce the risk of stress-related cardiac events.

Other choices such as increasing appetite, promoting sleep, or elevating blood sugar levels are not direct actions associated with beta-blockers. In fact, beta-blockers can sometimes have opposite effects on these processes, such as causing fatigue or changes in glucose metabolism.