GABA (gamma-aminobutyric acid) is the major inhibitory neurotransmitter in the central nervous system. There are two types of receptors for GABA, the GABAA who are members of the superfamily of ionotropic receptors (which are receptors for glycine and a-adrenergic receptors) and GABA B belonging to the superfamily of receptors coupled to protein G. Recently reported the existence of a third type of GABA receptor, called GABAC with different pharmacological properties, isolated from retinal neurons.