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.