Difference Between GABA A and GABA B

The key difference between GABA A and GABA B is that GABA A receptors are ligand-gated ion channels while GABA B receptors are G protein-coupled receptors.

Gamma-aminobutyric acid (GABA) is an inhibitory neurotransmitter in the brain. There are receptors for this GABA. GABA A and GABA B are two types of receptors. While GABA A receptors are ligand-gated ion channels, GABA B receptors are G protein-coupled receptors. GABA A and GABA B differ from each other due to several characteristics, as discussed in this article.

1. Overview and Key Difference
2. What is GABA A
3. What is GABA B
4. Similarities Between GABA A and GABA B
5. Side by Side Comparison – GABA A vs GABA B in Tabular Form
6. Summary

What is GABA A?

GABA A is one of the two types of receptors that bind with GABA. It is a ligand-gated Cl^– ion channel. In other words, it is an ionotropic receptor distributed mainly in the postsynaptic membrane of CNS. Furthermore, GABA A is a transmembrane receptor that is pentameric, having five subunits around a central core. The five subunits are two subunits of α, two subunits of β and one subunit of γ.

Figure 01: GABA A

GABA A is selectively permeable to Cl^– ions. Once this receptor binds with its ligand GABA, it becomes active and opens up its pore and allows Cl^– ions to pass through. However, depending on the action potential of the cell, Cl^– ions will flow out of/into the cell. Moreover, the influx of Cl- ions causes hyperpolarization of the neuronal membrane, leading to an inhibition of neurotransmission.

What is GABA B?

GABA B is another type of GABA receptors present in the brain. They are metabotropic receptors, which are G protein-coupled receptors. It is dimeric having two subunits.

Figure 02: GABA B

GABA B receptors are present both pre and postsynaptically. Similar to GABA A, GABA B is also a transmembrane receptor. Here, this receptor inhibits calcium channels and activates potassium channels. Moreover, it inhibits adenyl cyclase.

What are the Similarities Between GABA A and GABA B?

GABA A and GABA B are two classes of GABA receptors.
They bind with neurotransmitter gamma-aminobutyric acid.
Moreover, these two receptors are present in the central nervous system.
They are transmembrane receptors.
Also, both are widespread.
Besides, binding of GABA to both receptors causes inhibition of neurotransmission.

What is the Difference Between GABA A and GABA B?

GABA A and GABA B are two classes of GABA binding receptors. GABA A is a ligand-gated ion channel while GABA B is a G protein-coupled receptor. So, this is the key difference between GABA A and GABA B. Structurally, GABA A is a pentamer while GABA B is a dimer. Therefore, we can consider this also as a difference between GABA A and GABA B.

Moreover, a further difference between GABA A and GABA B is that the molecular weight of GABA A is 300 kDa, while the molecular weight of GABA B is 80 kDa.

The below infographic summarizes the difference between GABA A and GABA B.

Summary – GABA A vs GABA B

GABA A and GABA B are two GABA binding receptors. GABA A is a ligand-gated ion channel while GABA B is a G protein-coupled receptor. So, this is the key difference between GABA A and GABA B. Moreover, GABA A is a pentamer composed of five subunits, while GABA B is a dimer composed of two subunits. Furthermore, GABA A is distributed post-synaptically in the CAS while GABA B is distributed pre and post-synaptically in CNS. Thus, this summarizes the difference between GABA A and GABA B.

Reference:

1.“Gaba Receptors & Drugs Acting on Them.” LinkedIn SlideShare, 5 Jan. 2018, Available here.
2. “GABA Receptor.” Wikipedia, Wikimedia Foundation, 24 Sept. 2018, Available here.

Image Courtesy:

1. “Cell GABA Receptor” By BruceBlaus – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. GABAB-receptor1″ By Unknown – Украинская Википедия (Public Domain) via Commons Wikimedia