ABSTRACT
It was apparent that a third ß-adrenoreceptor (ßAR) existed some years before the cloning of the human ß3AR removed any remaining doubts (Emorine et al., 1989). Just as adrenoreceptors (ARs) had been classified into aARs and ßARs by Ahlquist, and ßARs into ß1-and ß2AR by Lands et al. (1967a,b), it was the availability of ligands which displayed a unique affinity or efficacy for the ß3AR that pointed to their existence. It was the availability of these ligands that also enabled the cloned ß3AR to be rapidly characterized, and its role in mammalian tissues to be understood.
