gamma-Aminobutyric acid

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gamma-Aminobutyric acid
GABA molecule
IUPAC name

4-aminobutanoic acid
Identifiers
CAS number 56-12-2 YesY
PubChem 119
ChemSpider 116 YesY
UNII 2ACZ6IPC6I YesY
DrugBank DB02530
KEGG D00058 YesY
MeSH gamma-Aminobutyric+Acid
ChEBI CHEBI:16865 YesY
ChEMBL CHEMBL96 YesY
IUPHAR ligand 1067
Jmol-3D images Image 1
Properties
Molecular formula C4H9NO2
Molar mass 103.12 g/mol
Appearance white microcrystalline powder
Density 1.11 g/mL
Melting point

203.7 °C, 477 K, 399 °F
Boiling point

247.9 °C, 521 K, 478 °F
Solubility in water soluble
Acidity (pKa) 4.23 (carboxyl), 10.43 (amino)[1]
Hazards
Main hazards Irritant, Harmful
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

γ-Aminobutyric acid (pron.: /ˈɡæmə əˈmiːnoʊbjuːˈtɪrɨk ˈæsɨd/ GAM-ə ə-MEE-noh-byew-TIRR-ik; or GABA /ˈɡæbə/) is the chief inhibitory neurotransmitter in the mammalian central nervous system. It plays a role in regulating neuronal excitability throughout the nervous system. In humans, GABA is also directly responsible for the regulation of muscle tone.[2]

Although chemically it is an amino acid, GABA is rarely referred to as such in the scientific or medical communities, because the term "amino acid," used without a qualifier, conventionally refers to the alpha amino acids, which GABA is not, nor is it ever incorporated into a protein.

In spastic diplegia in humans, GABA absorption becomes impaired by nerves damaged from the condition's upper motor neuron lesion, which leads to hypertonia of the muscles signaled by those nerves that can no longer absorb GABA.

Contents

Function [edit]

Neurotransmitter [edit]

In vertebrates, GABA acts at inhibitory synapses in the brain by binding to specific transmembrane receptors in the plasma membrane of both pre- and postsynaptic neuronal processes. This binding causes the opening of ion channels to allow the flow of either negatively charged chloride ions into the cell or positively charged potassium ions out of the cell. This action results in a negative change in the transmembrane potential, usually causing hyperpolarization. Two general classes of GABA receptor are known: GABAA in which the receptor is part of a ligand-gated ion channel complex, and GABAB metabotropic receptors, which are G protein-coupled receptors that open or close ion channels via intermediaries (G proteins).

The production, release, action, and degradation of GABA at a stereotyped GABAergic synapse

Neurons that produce GABA as their output are called GABAergic neurons, and have chiefly inhibitory action at receptors in the adult vertebrate. Medium Spiny Cells are a typical example of inhibitory CNS GABAergic cells. In contrast, GABA exhibits both excitatory and inhibitory actions in insects, mediating muscle activation at synapses between nerves and muscle cells, and also the stimulation of certain glands.[3] In mammals, some GABAergic neurons, such as chandelier cells, are also able to excite their glutamatergic counterparts.[4]

GABAA receptors are ligand-activated chloride channels; that is, when activated by GABA, they allow the flow of chloride ions across the membrane of the cell. Whether this chloride flow is excitatory/depolarizing (makes the voltage across the cell's membrane less negative), shunting (has no effect on the cell's membrane) or inhibitory/hyperpolarizing (makes the cell's membrane more negative) depends on the direction of the flow of chloride. When net chloride flows out of the cell, GABA is excitatory or depolarizing; when the net chloride flows into the cell, GABA is inhibitory or hyperpolarizing. When the net flow of chloride is close to zero, the action of GABA is shunting. Shunting inhibition has no direct effect on the membrane potential of the cell; however, it minimizes the effect of any coincident synaptic input essentially by reducing the electrical resistance of the cell's membrane (in essence, equivalent to Ohm's law). A developmental switch in the molecular machinery controlling concentration of chloride inside the cell – and, hence, the direction of this ion flow – is responsible for the changes in the functional role of GABA between the neonatal and adult stages. That is to say, GABA's role changes from excitatory to inhibitory as the brain develops into adulthood.[5]

Brain development [edit]

While GABA is an inhibitory transmitter in the mature brain, its actions are primarily excitatory in the developing brain.[5][6] The gradient of chloride is reversed in immature neurons, and its reversal potential is higher than the resting membrane potential of the cell; activation of a GABA-A receptor thus leads to efflux of Cl- ions from the cell, i.e. a depolarizing current. The differential gradient of chloride in immature neurons is primarily due to the higher concentration of NKCC1 co-transporters relative to KCC2 co-transporters in immature cells. GABA itself is partially responsible for orchestrating the maturation of ion pumps.[7] GABA-ergic interneurons mature faster in the hippocampus and the GABA signalling machinery appears earlier than glutamatergic transmission. Thus, GABA is the major excitatory neurotransmitter in many regions of the brain before the maturation of glutamateergic synapses.

However, this theory has been questioned based on results showing that in brain slices of immature mice incubated in artificial cerebrospinal fluid (ACSF) (modified in a way that takes into account the normal composition of the neuronal milieu in sucklings by adding an energy substrate alternative to glucose, beta-hydroxybutyrate) GABA action shifts from excitatory to inhibitory mode.[8]

This effect has been later repeated when other energy substrates, pyruvate and lactate, supplemented glucose in the slices' media.[9] Later investigations of pyruvate[10] and lactate[11] metabolism found that the original results were not due to energy source issues but to changes in pH resulting from the substrates acting as "weak acids". These arguments were later rebutted by further findings[12][13] showing that changes in pH even greater than that caused by energy substrates do not affect the GABA-shift described in the presence of energy substrate-fortified ACSF and that the mode of action of beta-hydroxybutyrate, pyruvate and lactate (assessed by measurement NAD(P)H and oxygen utilization) was energy metabolism-related.[14]

In the developmental stages preceding the formation of synaptic contacts, GABA is synthesized by neurons and acts both as an autocrine (acting on the same cell) and paracrine (acting on nearby cells) signalling mediator.[15][16] The ganglionic eminences also contribute greatly to building up the GABAergic cortical cell population. [17]

GABA regulates the proliferation of neural progenitor cells[18][19] the migration[20] and differentiation[21][7] the elongation of neurites[22] and the formation of synapses.[23]

GABA also regulates the growth of embryonic and neural stem cells. GABA can influence the development of neural progenitor cells via brain-derived neurotrophic factor (BDNF) expression.[24] GABA activates the GABAA receptor, causing cell cycle arrest in the S-phase, limiting growth.[25]

Beyond the nervous system [edit]

GABA-producing GAD67 enzyme in the brain slice at 1st postnatal day, with the highest expression in subventricular zone (svz). From Popp et al., 2009.[26]

GABAergic mechanisms have been demonstrated in various peripheral tissues and organs including, but not restricted to the intestine, stomach, pancreas, Fallopian tube, uterus, ovary, testis, kidney, urinary bladder, lung, and liver.[27]

In 2007, an excitatory GABAergic system was described in the airway epithelium. The system activates following exposure to allergens and may participate in the mechanisms of asthma.[28] GABAergic systems have also been found in the testis[29] and in the eye lens.[30]

Structure and conformation [edit]

GABA is found mostly as a zwitterion, that is, with the carboxy group deprotonated and the amino group protonated. Its conformation depends on its environment. In the gas phase, a highly folded conformation is strongly favored because of the electrostatic attraction between the two functional groups. The stabilization is about 50 kcal/mol, according to quantum chemistry calculations. In the solid state, a more extended conformation is found, with a trans conformation at the amino end and a gauche conformation at the carboxyl end. This is due to the packing interactions with the neighboring molecules. In solution, five different conformations, some folded and some extended, are found as a result of solvation effects. The conformational flexibility of GABA is important for its biological function, as it has been found to bind to different receptors with different conformations. Many GABA analogues with pharmaceutical applications have more rigid structures in order to control the binding better.[31][32]

History [edit]

Gamma-aminobutyric acid was first synthesized in 1883, and was first known only as a plant and microbe metabolic product. In 1950, however, GABA was discovered to be an integral part of the mammalian central nervous system.[33]

Synthesis [edit]

GABA does not penetrate the blood–brain barrier; it is synthesized in the brain. It is synthesized from glutamate using the enzyme L-glutamic acid decarboxylase and pyridoxal phosphate (which is the active form of vitamin B6) as a cofactor via a metabolic pathway called the GABA shunt. This process converts glutamate, the principal excitatory neurotransmitter, into the principal inhibitory neurotransmitter (GABA).[34][35]

Catabolism [edit]

GABA transaminase enzyme catalyzes the conversion of 4-aminobutanoic acid and 2-oxoglutarate into succinic semialdehyde and glutamate. Succinic semialdehyde is then oxidized into succinic acid by succinic semialdehyde dehydrogenase and as such enters the citric acid cycle as a usable source of energy.[36]

Pharmacology [edit]

Drugs that act as allosteric modulators of GABA receptors (known as GABA analogues or GABAergic drugs) or increase the available amount of GABA typically have relaxing, anti-anxiety, and anti-convulsive effects.[37][38] Many of the substances below are known to cause anterograde amnesia and retrograde amnesia.[39]

In general, GABA does not cross the blood–brain barrier,[40] although certain areas of the brain that have no effective blood–brain barrier, such as the periventricular nucleus, can be reached by drugs such as systematically injected GABA.[41] At least one study suggests that orally administered GABA increases the amount of Human Growth Hormone.[42] GABA directly injected to the brain has been reported to have both stimulatory and inhibitory effects on the production of growth hormone, depending on the physiology of the individual.[41]

GABAergic drugs [edit]

GABA as a supplement [edit]

A number of commercial sources sell formulations of GABA for use as a dietary supplement, sometimes for sublingual administration. These sources typically claim that the supplement has a calming effect. These claims are not yet scientifically proven. For example, there is evidence stating that the calming effects of GABA can be seen observably in the human brain after administration of GABA as an oral supplement.[48] However, there is also evidence that GABA does not cross the blood–brain barrier at significant levels.[40]

There are some over-the-counter supplements such as phenylated GABA itself directly, or Phenibut; and Picamilon (both Soviet cosmonaut products)--Picamilon combines niacin and phenylated GABA and crosses the blood–brain barrier as a prodrug that later hydrolyzes into GABA and niacin.[49]

In plants [edit]

GABA is also found in plants, where it is the most abundant amino acid in the apoplast of tomatoes.[50] It may also have a role in cell signalling in plants.[51][52]

See also [edit]

References [edit]

  1. ^ Dawson, R.M.C., et al., Data for Biochemical Research, Oxford, Clarendon Press, 1959.
  2. ^ Watanabe M, Maemura K, Kanbara K, Tamayama T, Hayasaki H (2002). "GABA and GABA receptors in the central nervous system and other organs". Int. Rev. Cytol. International Review of Cytology 213: 1–47. doi:10.1016/S0074-7696(02)13011-7. ISBN 978-0-12-364617-0. PMID 11837891. 
  3. ^ Ffrench-Constant RH, Rocheleau TA, Steichen JC, Chalmers AE (1993). "A point mutation in a Drosophila GABA receptor confers insecticide resistance". Nature 363 (6428): 449–451. Bibcode:1993Natur.363..449F. doi:10.1038/363449a0. PMID 8389005. 
  4. ^ Szabadics J, Varga C, Molnár G, Oláh S, Barzó P, Tamás G (January 2006). "Excitatory effect of GABAergic axo-axonic cells in cortical microcircuits". Science 311 (5758): 233–235. Bibcode:2006Sci...311..233S. doi:10.1126/science.1121325. PMID 16410524. 
  5. ^ a b Li K, Xu E (June 2008). "The role and the mechanism of gamma-aminobutyric acid during central nervous system development". Neurosci Bull 24 (3): 195–200. doi:10.1007/s12264-008-0109-3. PMID 18500393. 
  6. ^ Ben-Ari Y, Gaiarsa JL, Tyzio R, Khazipov R (October 2007). "GABA: a pioneer transmitter that excites immature neurons and generates primitive oscillations". Physiol. Rev. 87 (4): 1215–1284. doi:10.1152/physrev.00017.2006. PMID 17928584. 
  7. ^ a b Ganguly, K; Schinder, AF; Wong, ST; Poo, M (2001 May 18). "GABA itself promotes the developmental switch of neuronal GABAergic responses from excitation to inhibition.". Cell 105 (4): 521–32. doi:10.1016/S0092-8674(01)00341-5. PMID 11371348. 
  8. ^ Rheims S, Holmgren CD, Chazal G, Mulder J, Harkany T, Zilberter T, Zilberter Y (August 2009). "GABA action in immature neocortical neurons directly depends on the availability of ketone bodies". J. Neurochem. 110 (4): 1330–8. doi:10.1111/j.1471-4159.2009.06230.x. PMID 19558450. 
  9. ^ Holmgren CD, Mukhtarov M, Malkov AE, Popova IY, Bregestovski P, Zilberter Y (February 2010). "Energy substrate availability as a determinant of neuronal resting potential, GABA signaling and spontaneous network activity in the neonatal cortex in vitro". J. Neurochem. 112 (4): 900–12. doi:10.1111/j.1471-4159.2009.06506.x. PMID 19943846. 
  10. ^ Tyzio R, Allene C, Nardou R, Picardo MA, Yamamoto S, Sivakumaran S, Caiati MD, Rheims S, Minlebaev M, Milh M, Ferré P, Khazipov R, Romette JL, Lorquin J, Cossart R, Khalilov I, Nehlig A, Cherubini E, Ben-Ari Y (January 2011). "Depolarizing actions of GABA in immature neurons depend neither on ketone bodies nor on pyruvate". J. Neurosci. 31 (1): 34–45. doi:10.1523/JNEUROSCI.3314-10.2011. PMID 21209187. 
  11. ^ Ruusuvuori E, Kirilkin I, Pandya N, Kaila K (November 2010). "Spontaneous network events driven by depolarizing GABA action in neonatal hippocampal slices are not attributable to deficient mitochondrial energy metabolism". J. Neurosci. 30 (46): 15638–42. doi:10.1523/JNEUROSCI.3355-10.2010. PMID 21084619. 
  12. ^ Mukhtarov M, Ivanov A, Zilberter Y, Bregestovski P (January 2011). "Inhibition of spontaneous network activity in neonatal hippocampal slices by energy substrates is not correlated with intracellular acidification". J. Neurochem. 116 (2): 316–21. doi:10.1111/j.1471-4159.2010.07111.x. PMID 21083663. 
  13. ^ Ivanov A, Mukhtarov M, Bregestovski P, Zilberter Y (2011). "Lactate Effectively Covers Energy Demands during Neuronal Network Activity in Neonatal Hippocampal Slices". Front Neuroenergetics 3: 2. doi:10.3389/fnene.2011.00002. PMC 3092068. PMID 21602909. 
  14. ^ Khakhalin AS (May 2011). "Questioning the depolarizing effects of GABA during early brain development". J Neurophysiol 106 (3): 1065–7. doi:10.1152/jn.00293.2011. PMID 21593390. 
  15. ^ Purves D, Fitzpatrick D, Hall WC, Augustine GJ, Lamantia A-S (2007). Neuroscience (4th ed.). Sunderland, Mass: Sinauer. pp. 135, box 6D. ISBN 0-87893-697-1. 
  16. ^ Jelitai M, Madarasz E (2005). "The role of GABA in the early neuronal development" (PDF). Int. Rev. Neurobiol. International Review of Neurobiology 71: 27–62. doi:10.1016/S0074-7742(05)71002-3. ISBN 9780123668721. PMID 16512345. [dead link]
  17. ^ Marín & Rubenstein. (2001). A long, remarkable journey: Tangential migration in the telencephalon. Nature Reviews Neuroscience, 2.
  18. ^ LoTurco JJ, Owens DF, Heath MJ, Davis MB, Kriegstein AR (December 1995). "GABA and glutamate depolarize cortical progenitor cells and inhibit DNA synthesis". Neuron 15 (6): 1287–1298. doi:10.1016/0896-6273(95)90008-X. PMID 8845153. 
  19. ^ Haydar TF, Wang F, Schwartz ML, Rakic P (August 2000). "Differential modulation of proliferation in the neocortical ventricular and subventricular zones". J. Neurosci. 20 (15): 5764–74. PMID 10908617. 
  20. ^ Behar TN, Schaffner AE, Scott CA, O'Connell C, Barker JL (August 1998). "Differential response of cortical plate and ventricular zone cells to GABA as a migration stimulus". J. Neurosci. 18 (16): 6378–87. PMID 9698329. 
  21. ^ Barbin G, Pollard H, Gaïarsa JL, Ben-Ari Y (April 1993). "Involvement of GABAA receptors in the outgrowth of cultured hippocampal neurons". Neurosci. Lett. 152 (1–2): 150–154. doi:10.1016/0304-3940(93)90505-F. PMID 8390627. 
  22. ^ Maric D, Liu QY, Maric I, Chaudry S, Chang YH, Smith SV, Sieghart W, Fritschy JM, Barker JL (April 2001). "GABA expression dominates neuronal lineage progression in the embryonic rat neocortex and facilitates neurite outgrowth via GABA(A) autoreceptor/Cl- channels". J. Neurosci. 21 (7): 2343–60. PMID 11264309. 
  23. ^ Ben-Ari Y (September 2002). "Excitatory actions of gaba during development: the nature of the nurture". Nat. Rev. Neurosci. 3 (9): 728–739. doi:10.1038/nrn920. PMID 12209121. 
  24. ^ Obrietan K, Gao XB, Van Den Pol AN (August 2002). "Excitatory actions of GABA increase BDNF expression via a MAPK-CREB-dependent mechanism--a positive feedback circuit in developing neurons". J. Neurophysiol. 88 (2): 1005–15. PMID 12163549. 
  25. ^ Wang DD, Kriegstein AR, Ben-Ari Y (2008). "GABA Regulates Stem Cell Proliferation before Nervous System Formation". Epilepsy currents / American Epilepsy Society 8 (5): 137–139. doi:10.1111/j.1535-7511.2008.00270.x. PMC 2566617. PMID 18852839. 
  26. ^ Popp A, Urbach A, Witte OW, Frahm C (2009). "Adult and embryonic GAD transcripts are spatiotemporally regulated during postnatal development in the rat brain". In Reh, Thomas A. PLoS ONE 4 (2): e4371. Bibcode:2009PLoSO...4.4371P. doi:10.1371/journal.pone.0004371. PMC 2629816. PMID 19190758. 
  27. ^ Erdö SL, Wolff JR (1990). "gamma-Aminobutyric acid outside the mammalian brain". J. Neurochem. 54 (2): 363–372. doi:10.1111/j.1471-4159.1990.tb01882.x. PMID 2405103. 
  28. ^ Xiang, Y.; Wang, S.; Liu, M.; Hirota, J.; Li, J.; Ju, W.; Fan, Y.; Kelly, M. et al. (2007). "A GABAergic system in airway epithelium is essential for mucus overproduction in asthma". Nature Medicine 13 (7): 862–867. doi:10.1038/nm1604. PMID 17589520.   edit
  29. ^ Payne, Anita H.; Matthew H. Hardy (2007). The Leydig cell in health and disease. Humana Press. ISBN 1-58829-754-3, ISBN 978-1-58829-754-9 Check |isbn= value (help). 
  30. ^ Kwakowsky, A.; Schwirtlich, M.; Zhang, Q.; Eisenstat, D.; Erdélyi, F.; Baranyi, M.; Katarova, Z.; Szabó, G. (2007). "GAD isoforms exhibit distinct spatiotemporal expression patterns in the developing mouse lens: correlation with Dlx2 and Dlx5". Developmental dynamics : an official publication of the American Association of Anatomists 236 (12): 3532–3544. doi:10.1002/dvdy.21361. PMID 17969168.  edit
  31. ^ Majumdar Devashis, Guha Sephali (1988). "Conformation, electrostatic potential and pharmacophoric pattern of GABA (gamma-aminobutyric acid) and several GABA inhibitors". Journal of Molecular Structure: THEOCHEM 180: 125–140. doi:10.1016/0166-1280(88)80084-8. 
  32. ^ Anne-Marie Sapse. Molecular Orbital Calculations for Amino Acids and Peptides. Birkhäuser, 2000. ISBN 0-8176-3893-8.
  33. ^ Roth, Robert J.; Cooper, Jack R.; Bloom, Floyd E. (2003). The Biochemical Basis of Neuropharmacology. Oxford [Oxfordshire]: Oxford University Press. p. 106. ISBN 0-19-514008-7. 
  34. ^ Petroff OA (December 2002). "GABA and glutamate in the human brain". Neuroscientist 8 (6): 562–573. doi:10.1177/1073858402238515. PMID 12467378. 
  35. ^ Schousboe A, Waagepetersen HS (2007). "GABA: homeostatic and pharmacological aspects". Prog. Brain Res. Progress in Brain Research 160: 9–19. doi:10.1016/S0079-6123(06)60002-2. ISBN 978-0-444-52184-2. PMID 17499106. 
  36. ^ Alan W. Bown and Barry J. Shelp; Department of Biological Sciences, Brock University, St. Catharines, Ontario, Canada L2S 3A1 (A.W.B.); and Department of Horticultural Science, University of Guelph, Guelph, Ontario, Canada N1 G 2W1 (B.J.S.) (September 1997). "The Metabolism and Functions of y-Aminobutyric Acid". Plant Physiology 115 (1): 1–5. PMC 158453. PMID 12223787. 
  37. ^ Foster AC, Kemp JA (February 2006). "Glutamate- and GABA-based CNS therapeutics". Curr Opin Pharmacol 6 (1): 7–17. doi:10.1016/j.coph.2005.11.005. PMID 16377242. 
  38. ^ Chapouthier, G, Venault P., A pharmacological link between epilepsy and anxiety?, Trends in Pharmacological Sciences, 2001, 22(10), 491-493
  39. ^ Campagna, J. A.; Miller, K. W.; Forman, Stuart A. (22 May 2003). "Mechanisms of actions of inhaled anesthetics". New England Journal of Medicine 348 (21): 2110–2124. doi:10.1056/NEJMra021261. PMID 12761368. Retrieved 20 October 2011. 
  40. ^ a b Kuriyama K, Sze PY (January 1971). "Blood–brain barrier to H3-gamma-aminobutyric acid in normal and amino oxyacetic acid-treated animals". Neuropharmacology 10 (1): 103–108. doi:10.1016/0028-3908(71)90013-X. PMID 5569303. 
  41. ^ a b Müller EE, Locatelli V, Cocchi D (April 1999). "Neuroendocrine control of growth hormone secretion". Physiol. Rev. 79 (2): 511–607. PMID 10221989.  Free full-text.
  42. ^ Powers ME, Yarrow JF, McCoy SC, Borst SE (January 2008). "Growth hormone isoform responses to GABA ingestion at rest and after exercise". Medicine and science in sports and exercise 40 (1): 104–10. doi:10.1249/mss.0b013e318158b518. ISSN 1530-031. PMID 18091016. 
  43. ^ Dzitoyeva S, Dimitrijevic N, Manev H (2003). "Gamma-aminobutyric acid B receptor 1 mediates behavior-impairing actions of alcohol in Drosophila: adult RNA interference and pharmacological evidence". Proc. Natl. Acad. Sci. U.S.A. 100 (9): 5485–5490. Bibcode:2003PNAS..100.5485D. doi:10.1073/pnas.0830111100. PMC 154371. PMID 12692303. 
  44. ^ Mihic SJ, Ye Q, Wick MJ, Koltchine VV, Krasowski MD, Finn SE, Mascia MP, Valenzuela CF, Hanson KK, Greenblatt EP, Harris RA, Harrison NL (1997). "Sites of alcohol and volatile anaesthetic action on GABAA and glycine receptors". Nature 389 (6649): 385–389. Bibcode:1997Natur.389..385M. doi:10.1038/38738. PMID 9311780. 
  45. ^ Boehm SL, Ponomarev I, Blednov YA, Harris RA (2006). "From gene to behavior and back again: new perspectives on GABAAreceptor subunit selectivity of alcohol actions". Adv. Pharmacol. 54 (8): 1581–1602. doi:10.1016/j.bcp.2004.07.023. PMID 17175815. 
  46. ^ Dimitrijevic N, Dzitoyeva S, Satta R, Imbesi M, Yildiz S, Manev H (2005). "Drosophila GABAB receptors are involved in behavioral effects of gamma-hydroxybutyric acid (GHB)". Eur. J. Pharmacol. 519 (3): 246–252. doi:10.1016/j.ejphar.2005.07.016. PMID 16129424. 
  47. ^ "Bioassay-guided fractionation of lemon balm (Melissa officinalis L.) using an in vitro measure of GABA transaminase activity". Retrieved 2010-03-08. 
  48. ^ Abdou, Adham M.; Higashiguchi, S.; Horie, K.; Kim, Mujo; Hatta, H.; Yokogoshi, H. Biofactors. 2006, Vol. 26 Issue 3, p201-208. 8p. 4 Graphs. "Relaxation and immunity enhancement effects of gamma-aminobutyric acid (GABA) administration in humans." http://www.ncbi.nlm.nih.gov/pubmed/16971751
  49. ^ Dorofeev BF, Kholodov LE (1991). "[Pikamilon pharmacokinetics in animals]". Farmakologiia i toksikologiia (in Russian) 54 (2): 66–9. PMID 1884802. 
  50. ^ Park, D. H.; Mirabella, R.; Bronstein, P. A.; Preston, G. M.; Haring, M. A.; Lim, C. K.; Collmer, A.; Schuurink, R. C. (2010). "Mutations in γ-aminobutyric acid (GABA) transaminase genes in plants or Pseudomonas syringae reduce bacterial virulence". The Plant Journal 64 (2): 318–330. doi:10.1111/j.1365-313X.2010.04327.x. PMID 21070411. 
  51. ^ Bouché, N.; Fromm, H. (2004). "GABA in plants: Just a metabolite?". Trends in Plant Science 9 (3): 110–115. doi:10.1016/j.tplants.2004.01.006. PMID 15003233. 
  52. ^ Roberts, M. R. (2007). "Does GABA Act as a Signal in Plants? Hints from Molecular Studies". Plant Signaling & Behavior 2 (5): 408–582. doi:10.4161/psb.2.5.4335. 

External links [edit]

  • Lydiard B, Pollack MH, Ketter TA, Kisch E, Hettema JM (2001-10-26). "GABA". Continuing Medical Education. School of Medicine, Virginia Commonwealth University, Medical College of Virginia Campus (VCU), Richmond, VA. Retrieved 2008-06-20. "The role of GABA in the pathogenesis and treatment of anxiety and other neuropsychiatric disorders" 
  • Scholarpedia article on GABA
  • List of GABA neurons on NeuroLex.org
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