GABA_B receptors (GABA_BR) are metabotropic transmembrane receptors for gamma-aminobutyric acid (GABA) that are linked via G-proteins to potassium channels. The changing potassium concentrations hyperpolarize the cell at the end of an action potential. The reversal potential of the GABA_B-mediated IPSP is -100 mV, which is much more hyperpolarized than the GABA_A IPSP. GABA_B receptors are found in the central as well as in the autonomic division of the peripheral nervous system.