Neurotransmitters, such as glutamate, acetylcholine, serotonin, dopamine, norepinephrine, and gamma-aminobutyric acid (GABA), in the brain are important for the transmission of signals between neurons. In particular, GABA is the major inhibitory neurotransmitter. This means that the role of GABA in the brain is to counteract the action of excitatory neurotransmitters such as acetylcholine, promote relaxation, and decrease brain activity. When GABA in the brain reaches levels that are below normal or when GABA action is impaired, the neurons become overexcited, leading to excessive muscle contraction and a sense of restlessness.
GABA in the brain has the highest concentrations in areas such as the hypothalamus, hippocampus, and cortex. Neurons are separated by minute spaces called synapses through which a command or a signal travels to reach the next neuron. The neurons are not physically connected; therefore, GABA, as a brain neurotransmitter, acts like a molecular bridge. In particular, GABA binds to GABA receptors in the neuron’s plasma membrane, which results in the entry of chloride ions into the nerve cell or potassium ions out of the nerve cell. Approximately 30 to 40% of neural synapses have GABA.
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The role of GABA in the brain in promoting relaxation and in inhibiting excitation is important in understanding why drugs that enhance GABA action are used to treat several neurological or psychological disorders. For instance, during seizures, there is excessive activity in the brain cortex. To control seizures, drugs that act on GABA receptors are given, and examples of these GABAergic drugs, or GABA analogues, are benzodiazepines such as diazepam. Other drugs that simulate GABA action include flumanezil, barbiturates, and alcohol. Caffeine, on the other hand, neutralizes the actions of GABA, which is why coffee keeps people awake and active.
Other GABA uses include improvement of sleep cycles and reduction of blood pressure. Anxiety disorders may also benefit from GABAergic drugs. GABA may give symptomatic relief of back pain and arthritic conditions, and it may be used as a muscle tone regulator as well.
For people who have a deficiency of GABA, it may be given in the form of a dietary supplement, in 200 mg formulations. It is available in tablets and capsules, and may be taken four times a day, depending on the physician’s instructions. GABA does not generally cross from the blood to the brain, but it can enter near the spaces in the brain called ventricles. It has been said that if orally taken, GABA in the brain can increase the growth hormone and prolactin because of its effects on the pituitary gland.