Combining with the amino acid gamma-aminobutyric acid (GABA, 4-aminobutyrate) and transmitting the signal across the membrane by activating an associated G-protein; promotes the exchange of GDP for GTP on the alpha subunit of a heterotrimeric G-protein complex.
Source:
GOC:bf,
Wikipedia:GABAB_receptor,
IUPHAR_RECEPTOR:1276,
GOC:ai