The effects of beta (2)-adrenergic receptors activation on the cardiovascular system and on the skeletal muscle: A narrative review

Beta(2)-adrenergic receptors (adrenoceptors) are activated by the catecholamines norepinephrine and epinephrine. Adrenoceptors are found in different tissues, such as smooth muscle, skeletal muscle and myocardium. Stimulation of adrenoceptors is implicated in several physiological functions in the body, such as bronchodilation, increased perfusion and vasodilation. The latters, together with increased muscular mass and contraction speed, facilitate muscle's motility and contraction. In the cardiovascular system, the activation of adrenoceptors increases heart muscle contraction, cardiac output and heart rate. Some studies also suggested a cardioprotective role of the stimulation of adrenoceptors. Beta(2)-adrenergic receptors agonists, principally divided in long-acting beta(2) agonists (LABAs) and short-acting beta(2) agonists (SABAs), are primarily used to treat asthma and other pulmonary disorders. Beta(2)-adrenergic receptors activation has been correlated with anabolic properties and muscular hypertrophy with the use of oral clenbuterol, as well as intravenous albuterol. Given these anabolic, lipolytic and performance-enhancing effects, LABAs are frequently abused by athletes. For this reason, most of these drugs are banned by the World Anti-Doping Agency, or admissible only with limitations. The aim of this narrative review is to report the results of some recent studies about the effects of beta(2)-adrenergic receptors activation on the cardiovascular system and on the skeletal muscle.