An amino acid, it is probably the most common single (inhibitory) neurotransmitter of all, but it is not found in proteins. It has been estimated that 20-40% of all axon terminals in the brain contain GABA. Released into synaptic cleft, it can prevent the postsynaptic neuron from firing. This aids in ensuring that nerve cells do not fire too fast. GABA is synthesized from glutamate by means of the enzyme L-glutamic acid decarboxylase and pyridoxal phosphate (a derivative vitamin B6) as a cofactor, and involves converting the main excitatory neurotransmitter into the principal inhibitory one. There are three types of GABA receptors: GABAA (responsible for mediating the effects of GABA, GABAB (found in the central and autonomic nervous system, they can stimulate the opening of K+ channels that in turn brings the neuron closer to the equilibrium potential of K+, thereby hyperpolarizing the neuron, and thus preventing the sodium channels from opening and action potentials from firing), and GAB AC (mediate slow and sustained responses). The action of GABA decreases epileptic seizures and muscle spasms by inhibiting electrical signals in this manner. Moreover, there is evidence that the site of action in the brain of benzodiazepams, including Valium, is directly coupled to the brain receptor for GABA. GABA plays an important role in functioning of central pattern generators. For athletes, dietary GABA has attracted attention because it elevates growth hormone levels.
See Action potential, Attentional deficit hyperactivity disorder (ADHD), Basket cells, Central pattern generator (CPG), Golgi type II cells, Glutumate (or glutamate), Glycine, Neurotransmitters, Purkinje cells