GABAB-receptor isoforms: Molecular architecture and distribution

Abstract The slow component of GABAergic inhibition in the brain is mediated by the metabotropic GABA B -receptors. Most if not all GABA B -receptors are heterodimers of GABA B R1 (GBR1) and GABA B R2 (GBR2) proteins. Distinctive receptor isoforms are based on the presence of two GBR1 splice variants termed GBR1a and GBR1b. Both were found to be associated with GBR2 suggesting that the isoforms GBR1a/GBR2 and GBR1b/GBR2 represent the vast majority of GABA B -receptors in the brain. The two isoforms differed strikingly in their pattern of expression on the regional, cellular and subcellular level. These results point to distinct funcional roles of the two receptor isoforms.