Gamma-aminobutyric acid (GABA) is the main inhibitory mediator in the human nervous system. But only for those of us who have already developed it. And to give us a truly Olympian calm, it is sometimes aided by a motley company of very well-known substances. We’ll get to know GABA a little better and learn that this molecule is not as simple as it seems at first glance. What are GABA agonists: drugs for epilepsy?
The resting neurotransmitter
Gamma-aminobutyric acid (GABA) is synthesized in the brain from glutamic acid, another neurotransmitter, by decarboxylating it (removing the carboxyl group from the main chain). According to the chemical classification GABA is an amino acid, but not the usual one, that is, used for the synthesis of protein molecules, α-amino acid, where the amino group is attached to the first carbon atom in the chain. In GABA, the amino group is connected to the third atom from the carboxyl group (in glutamate it was first before decarboxylation).
To understand how this works, there are two things to consider. The first one is that one neuron can be affected by several oppositely directed forces at the same time: for example, five excitatory and three inhibitory neurons converged on one cell in this area of the nervous system. At the same time, they can affect the dendrite of this neuron and the axon in the presynaptic part. The second point is that the nerve cell experiencing these effects will work on an all-or-nothing basis. It cannot send a signal and not send a signal at the same time. All the influences of the signals coming to the cell are summed up, and if the resulting changes in the membrane potential exceed a certain value (called the excitation threshold), the signal will be transmitted to another cell through the synapse. If the threshold value is not reached, sorry – try again.
So, the GABA molecule binds to the ion channel receptor. The ion channel, which has a rather complicated structure, opens up and starts letting negatively charged chlorine ions inside the cell. Under the influence of these ions, the membrane is hyperpolarized, and the cell becomes less susceptible to excitatory signals from other neurons. This is probably the first and most important function of GABA, the inhibition of nerve cell activity in the nervous system. GABA is an inhibitory neurotransmitter that regulates many processes, from muscle tone to emotional reactions.