Abstract
The sympathetic system is central in the understanding of numerous physiological and physiopathological phenomena. During the last decade, the characterization of a new β-adrenoceptor subtype, β3, in addition to β1 and β2-adrenoceptor in the cardiovascular system has changed the view of the roles of the sympathetic system. In heart, β3-adrenoceptor stimulation produce an opposite effect to that induced by β1 and β2-adrenoceptors suggesting that in normal heart, the negative inotropic effect induced by the β3-adrenergic stimulation might play a role of a “safety-valve” during intense adrenergic stimulation. In vessels, all β-adrenoceptors subtypes, β1, β2 and β3, mediate a vasodilation. As β3-adrenoceptors are activated at higher concentrations of catecholamines than β1 and β2-adrenoceptors, they could play the roll of a receptor reserve. β3-adrenoceptors are overexpressed in heart failure and hypertension and could constitute a new therapeutic target. In addition, the efficiency of some β-blockers such as nebivolol could result from an action on β3-adrenoceptors.