Definition, structure and function
The Gamma (y) -Aminobuttersдure (short: GABA) is the most important inhibitory neurotransmitter in the central nervous system of mammals. In contrast to excitatory (excitatory) neurotransmitters such as glutamate, adrenaline or dopamine, GABA reduces the excitability of nerve cells.
As soon as a GABA molecule binds in a specific GABA receptor, ion channels open for chloride ions (Cl-) are permeable. As a result, the inflow of the negatively charged ions leads to hyperpolarization of the postsynaptic membrane (IPSP) and thus to the inhibition of the excitation. This principle applies at least to GABAaReceptors. Depending on the type of GABA receptor, there are differences in the way in which the inhibition works.
GABA is extracted in a human body from nonessential amino acid glutamic acid. Glutamic acid (C5H9NO4) is produced by glutamate decarboxylase in both brain and pancreas to GABA (C4H9NO2) decarboxylated. Within this process, the enzyme glutamate decarboxylase cleaves a carbon dioxide molecule (CO2) from amino acid.
In the brain, GABA is the most abundant neurotransmitter, accounting for about 1/3. Therefore, it is not surprising that sleep is essentially controlled by the inhibitory function of GABAergic neurons. Also medications such as narcotics or benzodiazepines for sleep initiation or anxiety reduction bind to the receptors of the y-aminobutyric acid and thus provide an inhibition of the excitement.
In the pancreas, the other place in the body in which GABA transmitters and receptors occur in larger quantities, the y-aminobutyric acid participates in the control of the blood sugar level. GABA controls there the inhibition of the secretion of the hormone glucagon, which is responsible for the rise of the blood sugar level.