Why say it three times? Because if you really try, you can attribute almost ANYTHING your body does to GABA (it might take a little creativity, but work with me here). It is a neurotransmitter with a receptor by the same name (If you are feeling cheated because no one was creative enough to make the name of the receptor more interesting, don’t fret. The people who name genes and chemical compounds have gone a little overboard). GABA (gamma-aminobutyric acid) receptors are mostly in the CNS, and they are responsible for managing neuronal action potentials that control everything from the sleep-wake cycle to memory.
For now, we will focus on the GABA-A (I just call them GABAAAAAAAH, but I’m not positive that is a generally accepted pronunciation) receptors, the hypothesized focus of a group of drugs known as anxiolytics, amnesics, and sedative hypnotics.
GABA-A receptors are a special type of ligand-gated chloride channel, and one of their particularly special functions is that they are inhibitory to neurons. That is, the influx of Cl- that they allow causes hyperpolarization, which reduces the possibility of an action potential. So if, say, you are having some issues with overactive neurons (like epilepsy), GABA-A agonists might be prescribed to calm those suckers down.
The other cool thing about GABA receptors is that, although their main ligand is GABA (and a few other compounds), they have all of these little ports called allosteric sites. Allosteric binding results in potentiation or inhibition of a receptor. In the case of GABA-A, potentiating allosteric sites can be bound by many of the drugs in the sedative hypnotic and antiepileptic classes, including benzodiazepines, barbituates, and vodka (well, alcohol).
Potentiation (agonism) of the GABA-A receptor has lots of useful actions. In anesthesia, it is used to make you sleepy and calm, to prevent nausea, and to help you forget much of what just happened to you (hallelujah!). In psychiatry, GABA-A potentiation is useful for temporarily reducing severe anxiety. In general medicine, GABA agonists are used to prevent seizures, stop status epilepticus (uncontrolled, continuous seizures), and as a sleep aid. As you can imagine, GABA antagonism results in quite the opposite reaction: increased neuronal activity and wakefulness.