Expression of GABA_B1 and GABA_B2 mRNA in the human brain

GABA_B receptors are widely expressed in the CNS. The distribution of the recently cloned GABA_B1 receptor is highly concordant with GABA_B ligand binding sites, but experiments with transfected cell lines indicate that GABA_B1 has to heterodimerize with GABA_B2 to gain the functionality of a native GABA_B receptor. Using in situ hybridization we investigated the expression of GABA_B1 and GABA_B2 mRNAs in the human brain. Both transcripts were detectable in prefrontal-cortex, hippocampus and cerebellum with no apparent mismatch, A distinct expression of GABA_B1 was detected in putative Bergmann glia. In the human striatum GABA_B1 mRNA was expressed in moderate amounts, whereas the GABA_B2 mRNA signal was not clearly above background. According to our data, the current concept on GABA_B receptor composition needs re-evaluation, at least for certain brain structures.