There is evidence for linkage of the power in the gamma band (29-45 Hz) of the resting electroencephalograph (EEG) over the frontal and central scalp with markers on chromosome 6q14-16 (Xuei et al., 2008). GABRR1 and GABRR2, encoding the GABA receptor subunits ρ1 and ρ2, lie together in a 137 kb region that falls within this linkage peak. Although the ρ1 and ρ2 subunits were originally found in the bipolar neurons in the retina (Cutting et al., 1991; Polenzani et al., 1991), they are widely expressed in the brain (including cortex, thalamus, pituitary gland, cerebellum, and hippocampus) and in the spinal cord (Cutting et al., 1991; Alakuijala et al., 2005a; Alakuijala et al., 2005b; Harvey et al., 2006; Lopez-Chavez et al., 2005; Milligan et al., 2004; Zheng et al., 2003). Homomeric ρ1 receptors are inhibited by ethanol at a low concentration (400 nM) of GABA (Mihic and Harris, 1996). Two amino acids in the GABA-A receptor transmembrane domains 2 (Ser270) and 3 (Ala291) are critical for allosteric modulation of the receptors by alcohols and volatile anesthetics (Mihic et al., 1997).
