Abstract: Nucleotidic sequences coding for the bovine adrenergic-.beta..sub.3 receiver (RA.beta..sub.3), utilization of said sequences as probes and for the expression of peptides and/or fragments thereof having an activity of bovine RA.beta..sub.3, vectors useful for said expression, as well as cellular hosts containing said vector. Polyclonal and monoclonal antibodies raised against said peptides and usable, particularly for the detection of bovine adrenergic-.beta..sub.3 receivers, as well as method for screening substances, with agonist or antagonist action in relation to peptides having an adrenergic-.beta..sub.3 receiver activity and kits for the detection of the affinity degrees of different substances for said peptides having an adrenergic-.beta..sub.3 receiver activity. Transgenic and recombinant mice containing said nucleotidic sequence.