Which of the following effects is associated with non-selective beta-blockers?

Non-selective beta-blockers act on both beta-1 and beta-2 adrenergic receptors. The beta-1 receptors are primarily located in the heart, and when these receptors are blocked, there is a significant reduction in heart rate and myocardial contractility. This leads to a decrease in cardiac output and can help manage conditions such as hypertension and heart failure.

In contrast, stimulation of beta-2 receptors results in bronchial dilation and smooth muscle relaxation in various tissues. Non-selective beta-blockers inhibit this effect, which is why they can have side effects related to respiratory function in susceptible individuals, particularly in asthmatics. Therefore, the correct choice reflects the primary action of non-selective beta-blockers on heart rate, which is a decrease, making it an important therapeutic effect in cardiovascular management.