The present invention provides an isolated GABAB 
receptor protein comprising at least one GABABR1a 
subunit and at least one GABABR2a 
subunit, characterized in that said GABAB 
receptor has one high affinity 
agonist binding site and one 
low affinity agonist binding site. In particular the isolated recombinant GABAB 
receptor protein expressed by the hGABABR1a / GABABR2 CHO 
cell line deposited at the Belgian Coordinated Collections of Microorganisms (BCCM) as CHO-K1 h-GABA-b R1a / R2 clone on Aug. 22, 2003 with the accession number LMBP 6046CB. It is thus an object of the present invention to provide the hGABABR1a / GABABR2 CHO 
cell line deposited at the Belgian Coordinated Collections of Microorganisms (BCCM) as CHO-K1 h-GABA-b R1a / R2 clone on Aug. 22, 2003 with the accession number LMBP 6046CB. The invention also provides the use of the aforementioned 
cell line in a method to identify GABAB receptor agonists using a functional or a binding 
assay. In particular in a 
radioligand-binding 
assay comprising the use of radiolabeled agonists such as for example 3H-GABA or 3H-
baclofen. In a particular embodiment the present invention provides the use of the aforementioned GABAB receptor in a method to identify a high affinity GABAB receptor 
agonist using a functional or a binding 
assay. In particular in a 
radioligand-binding assay comprising the use of radiolabeled agonists such as for example 3H-GABA or 3H-
baclofen. Alternatively, the aforementioned binding assays are performed on cellular extracts, in particular 
cellular membrane preparations of the aforementioned cells.