GABA(B) receptor heterodimer-component localisation in human brain

In recombinant cell lines, functional GABA, receptors are only formed by th e heterodimerisation between two related G-protein coupled receptor protein s GABA(B)R1 (GBR1) and GABA(B)R2 (GBR2), whilst the individual GBR1 or GBR2 do not produce fully functional receptors. To determine whether the hetero dimerisation occurs in vivo, novel polyclonal antibodies targeting the C te rmini of GBR1 and GBR2, were raised in different species, characterised, an d used to determine the relative localisation of the reported heterodimer c omponents in human brain tissue, using immunohistochemistry. The use of dif ferent species for the raising of the antisera allowed double immunofluores cent labelling of the receptors as an indication of GBR1/GBR2 receptor co-l ocalisation in human brain. The presence of both proteins is reported in ce rebellum, hippocampus, cortex, thalamus and basal ganglia. Regions of the b rainstem including pens and medulla, also express GBR1 and GBR2 protein. Th e double immunofluorescence demonstrated that GBR1 and GBR2 are co-localise d in the human cerebellar cortex. Together these results suggest the widesp read distribution of GABA(B) receptors in human brain, and that GABA(B) rec eptors GBR1 and GBR2 can exist in the same cell, and therefore may function as a heterodimer in the human brain. (C) 2000 Elsevier Science B.V. All ri ghts reserved.