Gamma-aminobutyric acid type B receptor subunit 1 (GABA-Receptor, R-2 subunit), together with the GABA-Receptor, R-1 subunit, forms a receptor for GABA. The activity of GABA-B-Receptor is mediated by G-proteins that inhibit adenylyl cyclase activity, stimulate phospholipase A2, activates potassium channels, inactivate voltage-dependent calcium-channels and modulate inositol phospholipids hydrolysis. The GABA-B-Receptor plays a critical role in the fine-tuning of inhibitory synaptic transmission. Pre-synaptic GABA-B-Receptors inhibits neurotransmitter release by down-regulating high-voltage activated calcium channels, whereas postsynaptic GABA-B-Receptor decrease neuronal excitability by activating a prominent inwardly rectifying potassium (Kir) conductance that underlies the late inhibitory postsynaptic potentials. The GABA receptor has not only been implicated in synaptic inhibition but also in hippocampal long-term potentiation, slow wave sleep, muscle relaxation and antinociception.