Functional GABA B receptors are heteromers of GABA B1 and B2 subunits, complexed with G protein alpha-i, 0, beta, and gamma subunits. They function as metabotropic receptors. When GABA is bound to the B1 sub-unit, the B2 subunit undergoes a conformational change that releases the G alpha-i G0 dimer (which binds and inactivates cytosolic adenylate cyclase) and the G beta G gamma dimer (which activates the GIRK (KIR3) potassium channel) (Pinard et al. 2010).