Gamma-aminobutyric acid is a neurotransmitter found in all mammals. It is also known as GABA or γ-Aminobutyric acid, using the Greek symbol for gamma. This substance is is the most important mammalian inhibitory neurotransmitter, and is utilized by the entire central nervous system (CNS). GABA's main function is to regulate neuronal excitation in the body. It does this by blocking impulses from one nerve to another, which, in turn, prevents nerves from over-firing.
Chemically, gamma-aminobutyric acid is an amino acid, but that designation is rarely applied to it. This is because the term 'amino acid' typically refers to any of the alpha amino acids, which are the essential building blocks of proteins in the body. GABA has no function in protein building, and therefore is usually referred to as simply an acid or neurotransmitter.
First synthesized in 1883, this acid was thought to exist only in plants and microbes. It was not until 1950 that gamma-aminobutyric acid was found to be an essential component of the CNS of all mammals. In these lifeforms, glutamate is used to synthesize GABA, via the use of the L-glutamic acid decarboxylase enzyme with a cofactor of active vitamin B6. The process creates gamma-aminobutyric acid, the body's chief inhibitory neurotransmitter, by altering glutamate, the body's primary excitatory neurotransmitter.
Mammalian muscle tone is regulated by GABA levels. A lack of GABA absorption in the legs, hips, and pelvis can result in a condition known as spastic diplegia or Little's disease. Without the inhibitory properties of gamma-aminobutyric acid absorption, muscles in the lower portion of the body become permanently hypertonic, or rigid, since the nerves would continually transmit the message to contract. The level of tension varies among individuals, with some able to walk with minimal trouble, and some requiring crutches or a cane to move.
GABAergic drugs are commonly used to treat anxiety or convulsive disorders. These act by either encouraging GABA receptors in the brain to release more of the neurotransmitter, or by causing an increase in the production of gamma-aminobutyric acid. The drugs have also been used to treat depression, bipolar disorder, and epilepsy. Both too little or too much GABA in the system can cause feelings of anxiety.
The oral use of the this acid has been shown to increase the amount of human growth hormone (HGH) in the body. Typically, GABAergic drugs do not cross the blood-brain barrier, unless they are directly injected into the brain. In that case, the effects of the drug on HGH may be either stimulating or depressing, depending on the individual's physiology.