GABA is the major inhibitory neurotransmitter in the mammalian brain where it acts at GABAA receptors, which are ligand-gatedchloride channels. Chloride conductance of these channels can be modulated by agents such as benzodiazepines that bind to the GABAA receptor. At least 16 distinct subunits of GABAA receptors have been identified. Transcript variants utilizing three different alternative non-coding first exons have been described.[1]
Subunit selective ligands
Recent research has produced several ligands which are moderately selective for GABAA receptors containing the α5 subunit. These have proved to be useful in investigating some of the side effects of benzodiazepine and nonbenzodiazepine drugs, particularly the effects on learning and memory such as anterograde amnesia. Inverse agonists at this subunit have nootropic effects and may be useful for the treatment of cognitive disorders such as Alzheimer's disease.
Basmisanil (RG-1662, RO5186582): derivative of Ro4938581, negative allosteric modulator at GABAA α5, in human trials for treating cognitive deficit in Down syndrome.[3]
↑Wingrove P, Hadingham K, Wafford K, Kemp JA, Ragan CI, Whiting P (February 1992). "Cloning and expression of a cDNA encoding the human GABA-A receptor alpha 5 subunit". Biochem. Soc. Trans. 20 (1): 18S. PMID1321750.
↑McCabe, L. L.; McCabe, E. R. B. (2013). "Down syndrome and personalized medicine: Changing paradigms from genotype to phenotype to treatment". Congenital Anomalies. 53 (1): 1–2. doi:10.1111/cga.12000. PMID23480351.
↑van Niel MB, Wilson K, Adkins CH, et al. (2005). "A new pyridazine series of GABAA alpha5 ligands". J. Med. Chem. 48 (19): 6004–11. doi:10.1021/jm050249x. PMID16162003.
↑Ballard TM, Knoflach F, Prinssen E, et al. (2008). "RO4938581, a novel cognitive enhancer acting at GABA(A) alpha5 subunit-containing receptors". Psychopharmacology. 202 (1–3): 207–23. doi:10.1007/s00213-008-1357-7. PMID18936916.
↑Chambers MS, Atack JR, Bromidge FA, et al. (2002). "6,7-Dihydro-2-benzothiophen-4(5H)-ones: a novel class of GABA-A alpha5 receptor inverse agonists". J. Med. Chem. 45 (6): 1176–9. doi:10.1021/jm010471b. PMID11881985.
↑Chambers MS, Atack JR, Broughton HB, et al. (2003). "Identification of a novel, selective GABA(A) alpha5 receptor inverse agonist which enhances cognition". J. Med. Chem. 46 (11): 2227–40. doi:10.1021/jm020582q. PMID12747794.
Further reading
Delong R (2007). "GABA(A) receptor alpha5 subunit as a candidate gene for autism and bipolar disorder: a proposed endophenotype with parent-of-origin and gain-of-function features, with or without oculocutaneous albinism". Autism. 11 (2): 135–47. doi:10.1177/1362361307075705. PMID17353214.
Otani K, Ujike H, Tanaka Y, et al. (2005). "The GABA type A receptor alpha5 subunit gene is associated with bipolar I disorder". Neurosci. Lett. 381 (1–2): 108–13. doi:10.1016/j.neulet.2005.02.010. PMID15882799.
Ritchie RJ, Mattei MG, Lalande M (1998). "A large polymorphic repeat in the pericentromeric region of human chromosome 15q contains three partial gene duplications". Hum. Mol. Genet. 7 (8): 1253–60. doi:10.1093/hmg/7.8.1253. PMID9668167.
Kim Y, Glatt H, Xie W, et al. (1997). "Human gamma-aminobutyric acid-type A receptor alpha5 subunit gene (GABRA5): characterization and structural organization of the 5' flanking region". Genomics. 42 (3): 378–87. doi:10.1006/geno.1997.4770. PMID9205108.
Glatt K, Glatt H, Lalande M (1997). "Structure and organization of GABRB3 and GABRA5". Genomics. 41 (1): 63–9. doi:10.1006/geno.1997.4639. PMID9126483.
Knoll JH, Sinnett D, Wagstaff J, et al. (1993). "FISH ordering of reference markers and of the gene for the alpha 5 subunit of the gamma-aminobutyric acid receptor (GABRA5) within the Angelman and Prader–Willi syndrome chromosomal regions". Hum. Mol. Genet. 2 (2): 183–9. doi:10.1093/hmg/2.2.183. PMID8388764.
Russek SJ, Farb DH (1995). "Mapping of the beta 2 subunit gene (GABRB2) to microdissected human chromosome 5q34-q35 defines a gene cluster for the most abundant GABAA receptor isoform". Genomics. 23 (3): 528–33. doi:10.1006/geno.1994.1539. PMID7851879.
Glatt KA, Sinnett D, Lalande M (1993). "Dinucleotide repeat polymorphism at the GABAA receptor alpha 5 (GABRA5) locus at chromosome 15q11-q13". Hum. Mol. Genet. 1 (5): 348. doi:10.1093/hmg/1.5.348. PMID1338907.
Wingrove P, Hadingham K, Wafford K, et al. (1992). "Cloning and expression of a cDNA encoding the human GABA-A receptor alpha 5 subunit". Biochem. Soc. Trans. 20 (1): 18S. PMID1321750.
