Anatomy & Organs

GABA receptor – structure, function & diseases

GABA receptor

GABA receptors are located in the nervous system and bind to the neurotransmitter γ-aminobutyric acid . By binding, they show an inhibitory effect on nerve cells . The targeted administration of certain drugs can affect the receptors and thus also the nerve cells, which is relevant for the treatment of epilepsy , for example.

What is a GABA receptor?

The receptors are sensory cells to which certain stimuli can bind. For example, in the perceptual structures, receptors are the first instance of each perception. These structures also play an important role in many other bodily processes.

For example, the human nervous system is equipped with GABA receptors. The so-called neurotransmitters bind to these receptors. These substances are neurogenic substances and thus correspond to messenger substances. The binding of the messenger substances to a GABA receptor shows an inhibitory effect on the associated nerve cell. A distinction is made between ionotropic and metabotropic GABA receptors. In addition to the GABAA receptor, the GABAC receptor is one of the ionotropic binding sites.

A metabotropic receptor is the GABAB receptor. The exact mode of action of GABA receptors depends on the particular subgroup. The ionotropic variants are ligand-controlled and therefore affect the ion and electrolyte balance. The influx of ions within a signaling cascade occurs, for example, through the activation of ionotropic GABA receptors. The metabotropic receptors act on metabolic processes and activate the formation of secondary messenger substances within the signal cascade after stimulus binding.

Anatomy & Structure

All GABA receptors in the human nervous system are located on one nerve cell each. Each of the receptors is a so-called transmembrane protein. Transmembrane proteins correspond to integral membrane proteins with one or more transmembrane domains.The lipid bilayer for spanning integral membrane proteins is called the transmembrane domain. Receptors are equipped with structures to which certain substances can bind. Due to the fixed structure of their binding sites, all GABA receptors only react to specific influences and are therefore only able to bind to certain messenger substances or neurotransmitters. The receptors specifically bind the neurotransmitter γ-aminobutyric acid in particular. Unlike the other subgroups of GABA, the GABAB receptor is a G protein-coupled receptor that can be located either pre- or postsynaptically.

GABAA receptors correspond to ligand-activated ion channels that are permeable to hydrogen and chloride carbonate ions. They are heteropentamers and thus each consist of five subunits, each of which spans the cell membrane four times. Homologous subunits are the six representatives α1 to α6, the three representatives β1 to β3, the three representatives γ1 to γ3 and δ, ε, π or θ, each with one representative. ρ has three representatives from ρ1 to ρ3. In the brain, the receptors are usually made up of two α, two β and one γ subunit. In addition to the γ-aminobutyric acid binding site, GABAA receptors possess allosteric binding sites which are responsive to benzodiazepines and are located on the γ subunit. Binding sites for neurosteroids and barbiturates are located on the β subunit.

Function & Tasks

GABA receptors are either ligand-gated or metabotropic. The ligand-gated receptors include the GABAA and GABAC receptors. Only the GABAB receptor is metabotropic. The ligand-gated GABAA receptor is a chloride ion channel. When it binds to GABA, Cl- flows in. This influx shows an inhibitory effect on the nerve cell. These subvariants are widespread in the brain and are responsible for the balance between excitation and attenuation in nerve cells .

Central nervous depressants such as benzodiazepines, propofol or antiepileptics bind to these receptors. The ligand-gated GABAA-ρ receptor cannot be inhibited by bicuculline. This means that active ingredients such as antiepileptics have hardly any effect on these areas. The metabotropic GABAB receptor is found either presynaptically or postsynaptically. When GABA binds to presynaptic receptors, more K+- flows in. The influx of Ca2+ decreases. This leads to hyperpolarization: the release of the transmitter is thus inhibited.

Upon binding to the postsynaptic variant, increased K+ influx is activated. This is how the inhibitory postsynaptic potential arises. This type of GABA receptor is sensitive to substances such as the muscle relaxant baclofen . GABAA receptors are collectively distributed in the brain and spinal cord , where they are some of the most important receptors for inhibition of the central nervous system . In the basal ganglia and cerebellum , these receptors are involved in motor control.

In the thalamus , receptors help initiate and maintain sleep. In the spinal cord, GABA receptors are located on the motor neurons , where they are involved in reflex wiring and the coordination of movements.

Diseases

The GABA receptors are clinically and pharmacologically relevant primarily in connection with the substances that can bind to them. This applies to alcohol , for example .Alcoholic beverages bind to the GABAA receptors and increase the permeability for chloride ions on the nerve cell membrane. This leads to hyperpolarization and the action potential frequency decreases. Because the excitatory system is simultaneously inhibited due to the binding of alcohol to NMDA receptors, alcohol has a sedative effect on humans. This association may be relevant in alcohol intoxication and is also an important association in clinical practice in chronic alcohol abusers.

Apart from that, the state of the central nervous system can be influenced by pharmacological substances that are able to bind to the GABA receptors. This plays an important role in clinical practice in the treatment of various neurological diseases. The treatment of epilepsy, for example, builds on this connection, but in general the targeted influencing of the nervous system through the administration of medication is a main component of therapy. Tranquilizers such as benzodiazepines have a sedative effect. The same applies to barbiturates, which are often used to induce anesthesia .

Antiepileptic drugs such as valproate prevent epileptic seizures by inhibiting the receptors. Tiagabine inhibits the reuptake of GABA and increases its concentration in the synaptic cleft, reducing epileptic seizures. Many drugs also have a stimulating effect on GABAA receptors and can thus trigger addictions. Addiction is mediated via α1-containing receptors. Their irritation causes functional changes in certain AMPA receptors of the respective neuron in neuroplastic processes.

Typical & common diseases of the central nervous system

Website | + posts

Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.