A second member of the class C family of GPCRs comprises the GABA-B receptors (GABAB1-3): metabotropic transmembrane receptors for gamma-aminobutyric acid (GABA) that are linked via G-proteins to potassium channels. They can stimulate the opening of K+ channels which brings the neuron closer to the equilibrium potential of K+, hyperpolarizing the neuron. This prevents sodium channels from opening, action potentials from firing, and VDCCs from opening, and so stops neurotransmitter release. Thus GABAB receptors are considered inhibitory receptors.
 The ‘ABC’of GABA receptors: a brief review. M. Chebib, G.A.R. Johnston. Clin. Exp. Pharmacol. Physiol. 1999, 26, 937-940