Two GABA(B) receptor subunits have been cloned: GABA(B1) and GABA(B2). In this study we investigate the coupling of recombinant GABA(B) receptors to calcium channels in differentiated NG108-15 cells, which exhibit many similarities to neurones but in which functional GABA(B) receptors are normally absent. Transfection of GABA(B1) and GABA(B2) subunit cDNAs enables baclofen-mediated inhibition of different calcium channel subtypes and a component of this modulation is voltage-dependent. When transfected individually, GABA(B2), but not GABA(B1), is able to enhance calcium current inhibition over background levels. Further, an antisense oligodeoxynucleotide to GABA(B1) reduces the average functional response in cells transfected with GABA(B2) alone. Assuming that the functional receptor is heteromeric, this suggests that GABA(B1), but not GABA(B2), is expressed endogenously in NG108-15 cells.