Activation of gamma-aminobutyric acid(B) (GABA(B)) receptors in dorsal root ganglion (DRG) neurones leads to inhibition of calcium (Ca(2+)) channels. The role of the GABA(B1) receptor subunit was assessed by its depletion achieved by microinjection of DRG neurones with an antisense (A/S) oligodeoxynucleotide (ODN). Control neurones were injected with a scrambled version of the A/S ODN (missense) or were not injected. Patch clamp recordings of Ca(2+) channel current were made two to four days after injection. GABA(B1) A/S substantially reduced the current inhibition induced by baclofen, a GABA(B) agonist. Therefore, most, if not all, native GABA(B) receptors which couple to Ca(2+) channels contain GABA(B1). Moreover, if native receptors are heterodimers of GABA(B1) and GABA(B2), then GABA(B2), in isolation, is unable to sustain coupling to Ca(2+) channels.