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.

CONTENTS

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.

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.

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