What is the primary characteristic of beta blockers?

Beta blockers primarily function by inhibiting the action of catecholamines, such as epinephrine and norepinephrine, at the beta-adrenergic receptors in the body. This action leads to various physiological effects, including decreased heart rate and lower blood pressure, making them effective in managing conditions like hypertension and anxiety. They reduce the heart's workload and oxygen demand, particularly during stress.

The other options describe functions that are contrary to what beta blockers do. For example, stimulating adrenergic receptors and enhancing catecholamine effects are actions associated with agonists, which increase the activity of these neurotransmitters rather than blocking them. Similarly, increasing metabolic rates typically relates to stimulatory drugs or hormones, which is not characteristic of the beta-blocking action. These aspects highlight the significance and specificity of beta blockers in pharmacology and clinical practice.