GABA is important in the treatment of anxiety. GABA is the main fast inhibitory neurotransmitter, counterbalancing the excitatory transmission by adrenaline and other neurotransmitters. This can be done by using an allosteric modulator for the GABA_A receptor, such as benzodiazepines and barbiturates.
An allosteric modulator does not activate the receptor, but instead binds at the orthosteric site, modulating the receptor’s response to an agonist binding the allosteric site. Benzodiazepines are positive allosteric modulators (PAM) of GABA_A, making the receptor more easily excitable. This leads to more frequent opening of the channel and therefore higher levels of inhibitory nervous transmission. This allows GABA and benzodiazepine to have a greater response than GABA alone.
GABA_A receptors are ionotropic, formed of five subunits. As they are found post-synaptically, they excite the post-synaptic neurone on activation by GABA. Other compounds are able to bind to GABA_A receptors as agonists (muscimol, …) and antagonists (bicuculine, picrotoxin, …) to control the activation of the receptor.