Located in gamma-aminobutyric acid (GABA) are receptors called GABAA receptors. The inhibitory effect of GABA is regulated by these GABAA receptors, which cause there to be less excitatory stimuli in the brain. The sedating and calming effect of GABA is due to these special receptors. One’s muscle tone and susceptibility to seizure is also affected by GABA. Many anti-depression and anti-anxiety drugs are able to be effective by binding to GABAA receptors.
GABA is present in the brain of a plethora of higher animals, as a significant 40% of all synapses in mammals have the necessary receptors for it. It is released into the synapse from a neuron, and is then bound to receptors in the cells close by. Located in the cell membrane, the GABAA receptors are classified as channel or ionotropic receptors. Once bound with GABA, these cells will develop an opening, wherein a channel for negatively charged ions flow into the opened cell. This affects the charge and lowers the electrical excitably and capability of reacting with other cells.
GABAA receptors can be classified into a variety of subtypes, which can also vary in the composition of the individual subunits of protein. As a result of this receptor being the target of a variety of crucial sedative drugs, each of which must bind to a specific part of the receptor, GABAA subtypes have been classified by pharmacologists in accordance with the way each compound attaches to them. For example, a type of muscle relaxants known as benzodiazepines attach to specific protein locations on the GABA receptors that differ from the protein locations on GABA itself. Some anesthetics as well as Ethanol are similar in that they also have their own specific protein binding locations on GABAA receptors.
Neuronal feedback loops monitor and regulate neural signals throughout one’s body as well as excitatory neurotransmitters, and GABAA receptors are an integral part of this process. GABA is able to regulate muscle tone by limiting uncontrolled spastic movements. When benzodiazepines attach themselves to GABAA receptors, they negate spasms and cramps by starting this feedback loop. As a result of the sedative qualities of GABA, these drugs can also trigger a deep sense of drowsiness and reduction in precise motor control.
By controlling neural inhibition in the peripheral and central nervous system, GABA is able to regulate where and when neurons are active. In other words, when neurons are stimulated in the brain, such as in the case of epileptic seizures, activating GABA receptors can eliminate the seizure. Some barbiturates and other such anti-convulsive drugs work in this manner, as well as anti-anxiety drugs that work by activating GABAA receptors.
Photo credit: 江舟孤雪
Article of interest: GABA’s Role in the Brain