Gamma-aminobutyric acid
From Freepedia
Gamma-aminobutyric acid (GABA) is a neurotransmitter in widely divergent species.
| Gamma-aminobutyric acid | |
|---|---|
| Image:GABA.gif | |
| General | |
| Systematic name | 4-aminobutanoic acid |
| Other names | GABA |
| Molecular formula | C4H9NO2 |
| SMILES | C(CC(=O)O)CN |
| Molar mass | 103.12 g/mol |
| Appearance | ? |
| CAS number | 56-12-2 |
| Properties | |
| Density and phase | ? g/cm3, ? |
| Solubility in water | ? g/100 ml (? °C) |
| Melting point | ? °C (? K) |
| Boiling point | ? °C (? K) |
| Acidity (pKa) | ? |
| Basicity (pKb) | ? |
| Chiral rotation [α]D | ?° |
| Viscosity | ? cP at ? °C |
| Structure | |
| Molecular shape | ? |
| Coordination geometry | ? |
| Crystal structure | ? |
| Dipole moment | ? D |
| Hazards | |
| MSDS | External MSDS |
| Main hazards | ? |
| NFPA 704 | |
| Flash point | ? °C |
| R/S statement | R: ? S: ? |
| RTECS number | ? |
| Supplementary data page | |
| Structure and properties | n, εr, etc. |
| Thermodynamic data | Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Other anions | ? |
| Other cations | ? |
| Related ? | ? |
| Related compounds | ? |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references | |
In humans, GABA acts at inhibitory synapses in the brain and spinal cord. As in the other contexts where GABA acts as a transmitter, the inhibition results from a hyperpolarization of the transmembrane potential of the inhibited neuron, which is elicited by the binding of GABA molecules to specific receptors in the plasma membrane of both pre- and post-synaptic cells. This binding opens ion channels to allow either the flow of chloride or potassium ions into or out of the cell.
In insects, GABA mediates muscle activation at synapses between nerves and muscle cells and also the stimulation of certain glands. So far three general classes of GABA receptor are known, more than one of which is often represented in the same organisms. These include both so-called ionotropic receptors, which are ion channels themselves, and metabotropic receptors, which are G protein-coupled receptors that open ion channels via intermediaries (G proteins).
With regard to the human brain, it has been asserted that GABA signals interfere with the registration and consolidation stages of memory formation. This is thought to be possible because the GABA system is found in the hippocampus, an area of brain which has been implicated in memory formation.
Organisms synthesize GABA from glutamate using the enzyme L-glutamic acid decarboxylase and pyridoxal phosphate as a cofactor. It is worth noting that this involves converting the principal excitatory neurotransmitter into the principal inhibitory one.
Three types of GABA receptors:
Drugs which affect GABA receptors:
- alcohol
- bicuculline
- benzodiazepines and barbiturates
- baclofen
- carbamazepine, phenytoin, valproate
- gabazine (SR-95531)
- gamma-hydroxybutyrate (GHB)
- picrotoxin
- propofol
- thujone
- zolpidem, zopiclone
- progabide
Drugs which affect GABA in other ways:
- tiagabine - potentiates by inhibiting uptake into neurons and glia.
- vigabatrin - potentiates by inhibiting GABA-T, preventing inactivation.
