The expression of GABA(B1) and GABA(B2) receptor subunits in the CNS differs from that in peripheral tissues

GABA(B) receptors are G-protein-coupled receptors that mediate the slow and prolonged synaptic actions of GABA in the CNS via the modulation of ion ch annels. Unusually, GABA(B) receptors form functional heterodimers composed of GABA(B1) and GABA(B2) subunits. The GABA(B1) subunit is essential for li gand binding, whereas the GABA(B2) subunit is essential for functional expr ession of the receptor dimer at the cell surface. We have used real-time re verse transcriptase-polymerase chain reaction to analyse expression levels of these subunits, and their associated splice variants, in the CNS and per ipheral tissues of human and rat. GABA(B1) subunit splice variants were exp ressed throughout the CNS and peripheral tissues, whereas surprisingly GABA (B2) subunit splice variants were neural specific. Using novel antisera spe cific to individual GABA(B) receptor subunits, we have confirmed these find ings at the protein level. Analysis by immunoblotting demonstrated the pres ence of the GABA(B1) subunit, but not the GABA(B2) subunit, in uterus and s pleen. Furthermore, we have shown the first immunocytochemical analysis of the GABA(B2) subunit in the brain and spinal cord using a GABA(B2)-specific antibody. We have, therefore, identified areas of non-overlap between GABA(B1) and GA BA(B2) subunit expression in tissues known to contain functional GABA(B) re ceptors. Such areas are of interest as they may well contain novel GABA(B) receptor subunit isoforms, expression of which would enable the GABA(B1) su bunit to reach the cell surface and form functional GABA(B) receptors. (C) 2000 IBRO. Published by Elsevier Science Ltd. All rights reserved.