Recombinant GABA_B receptors formed from GABA_B1 and GABA_B2 Subunits selectively inhibit N-type Ca^2+ Channels in NG108-15 Cells

Efficient transfection of NG108-15 cells with GABA(B) receptor subunits was achieved using polyethylenimine. Baclofen modulated high voltage-activated Ca2+ current in differentiated cells transfected with GABA(B1) and GABA(B2) receptor subunits or with the GABA(B2) subunit alone, but not with the GABA(B1) subunit alone. Characteristics of the current modulation were very similar for cells transfected with GABA(B1.2) and GABA(B2) subunits. Using antisense oligonucleotides against GABA(B1) subunits and also western immunoblotting, we are able to show that NG108-15 cells contain endogenous GABA(B1) subunits. Therefore, functional receptors can be formed by the combination of native GABA(B1) subunits with transfected GABA(B2) subunits, in agreement with the proposed heteromeric structure of GABA(B) receptors, Finally, we used selective channel blockers to identify the subtypes of Ca2+ channels that are modulated by GABA(B) receptors. In fact, in differentiated NG108-15 cells, the recombinant GABA(B) receptors couple only to N-type Ca2+ channels. (C) 2002 Elsevier Science B.V All rights reserved.