GABA

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GABA, also know as gamma-Aminobutyric acid, is the main inhibitory neurotransmmitter found in the central nervous system of vertebrates[1]. The main function of GABA is to reduce neuronal activity in the nervous system. It is referred to as 4-aminobutanoic acid via the IUPAC nomenclature. The neurotransmitter binds to transmembrane receptors on the plasma membrane on postsynaptic neurones. This either results in the flow of negatively charges chloride ions into the neurone or the flow of positively charged potassium ions outside of the neurone. Either of these actions results in hyperpolarisation of the postsynaptic neurone, so no further action potentials can be fired. This works by the GABA altering permeability of membranes to chloride ions or potassium ions. Either chloride ion channels will be opened and chloride ions will diffuse into the neurone down the concentration gradient or potassium ion channels will open causing potassium ions to diffuse out of the neurone down the concentration gradient. Either movement of ions will cause the membrane potential to decrease so much that an action potential can no longer be propagated as it is too difficult for the membrane to increase its potential voltage and exceed the threshold for the action potential. However, in insects, the effects of GABA have the additional effects of being excitatory as well and inhibitory, resulting in the stimulation of muscle and glands[2]. GABA is involved in many processes in the body for example, in the reduction of anxiety and pain, GABA is like our internal ‘calming mechanism’ by having an inhibitory effect on our neuronal pathways and decreasing stimulation of other neurotransmitters. For example, noradrenaline and adrenaline can be released in response to stressful situations and cause certain groups of neurons to become very active and fire action potentials very rapidly, GABA will have an inhibitory effect on these[3].

GABA is also heavily involved in sleep. In the brain there’s a bundle of cells known as the VLPO (ventrolateral preoptic nucleus), approximately 80% of the cells in the VLPO specialize in GABA transmission. This VPO is often referred to as the ‘sleep switch’. GABA is also known to be involved in many other processes such as memory formation and maintenance and is known to be a contributor to disorders such as depression and anxiety. GABA is important in the selective re-uptake of a neurotransmitter called Serotonin. Serotonin is known to be associated with positive moods and ‘happy’ feelings. If someone doesn’t have enough GABA they will not get enough serotonin reuptake and it can lead to depressive moods[4].

References

  1. Book: GABA and GABA receptors in the central nervous system and other organs, page 1, 2002
  2. GABA Receptors of Insects, David B. Sattelle, 1990, Available from: http://www.sciencedirect.com/science/article/pii/S0065280608600053#!
  3. Eugene Roberts (2007) Gamma-aminobutyric acid. Scholarpedia, 2(10):3356.. Available from http://www.scholarpedia.org/article/Gamma-aminobutyric_acid
  4. https://examinedexistence.com/what-does-the-neurotransmitter-gaba-do/
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