“…The contacts of ligands on this secondary binding site have implications for the down-regulation of β 1 ARs and the response in the myocardium. 92 Indeed, studies with compounds that contact this binding site, specifically carvedilol and bucindolol (for which contacts have been demonstrated through X-ray crystal structures), have yielded insights into their probable role. 93 Initially, these compounds were only proposed as β-blockers.…”