β3 -AR and the vertebrate heart: a comparative view

Recent cardiovascular research showed that, together with b1- andb2-adrenergic receptors (ARs), b3-ARs contribute to the catecholamine(CA)-dependent control of the heart. b3-ARs structure, function and ligands were investigated in mammals because of their applicative potential in human cardiovascular diseases. Only recently, the concept of a b3-AR-dependent cardiac modulation was extended to non-mammalian vertebrates, although information is still scarce and fragmentary. b3-ARswere structurally described in fish, showing a closer relationship to mammalianb1-AR than b2-AR. Functional b3-ARs are present in the cardiac tissue of teleosts and amphibians. As in mammals, activation of thesereceptors elicits a negative modulation of the inotropic performance through the involvement of the endothelium endocardium (EE), Gi/0 proteinsand the nitric oxide (NO) signalling. This review aims to comparatively analyse data from literature on b3-ARs in mammals, with those on teleosts and amphibians. The purpose is to highlight aspects of uniformityand diversity of b3-ARs structure, ligands activity, function and signallingcascades throughout vertebrates. This may provide new perspectives aimed to clarify the biological relevance of b3-ARs in the context of of the nervous and humoral control of the heart and its functional plasticity.