What is the Difference Between D1 and D2 Receptors

The key difference between D1 and D2 receptors is that the D1 receptor is a protein that regulates memory, attention, impulse control, renal function, and locomotion in humans, while the D2 receptor is a protein that regulates locomotion, attention, sleep, memory, and learning in humans.

Dopamine receptors are a class of G protein-coupled receptors. They are prominently present in the vertebrate central nervous system (CNS). They activate different effectors through G protein coupling as well as coupling with different protein interactions. Dopamine is the primary endogenous ligand for dopamine receptors. These receptors are used in different processes, including motivational salience, cognition, memory learning, fine motor control, and neuroendocrine signaling. D1 and D2 Receptors are two main types of dopamine receptors.

1. Overview and Key Difference
2. What are D1 Receptors
3. What are D2 Receptors
4. Similarities – D1 and D2 Receptors
5. D1 vs D2 Receptors in Tabular Form
6. Summary – D1 vs D2 Receptors

What are D1 Receptors (DRD1)?

The D1 receptor is also known as DRD1. It is one of the two types of receptors in the D1-like receptor family. The other receptor in this family is D5. It is a protein present in humans and is encoded by a gene called the DRD1 gene. It is detected through the northern blot technique and in-situ hybridization. The D1 receptor is mainly expressed in the dorsal striatum and ventral striatum. The low levels of expression of this protein can be found in the basolateral amygdala, cerebral cortex, septum, thalamus, and hypothalamus. D1 receptor normally regulates the memory, learning, and growth of neurons. Moreover, it is also used in the reward system and locomotor activity, mediating some behaviours and modulating dopamine receptor d2-mediated events.

A D1 receptor is primarily produced in the caudate putamen in humans and caudate putamen, nucleus accumbens, and olfactory tubercle in the mouse. Furthermore, dihydrexidine (A-86929, dihydrexidine, dinapsoline, etc.) and benzazepine (SKF-81297, SKF-82958, SKF-38393, etc.) derivatives are the main agonists for DI receptors. Ecopipam, on the other hand, is a selective antagonist of the D1 receptor.

What are D2 Receptors?

The D2 receptor is a protein that regulates locomotion, attention, sleep, memory, and learning. This protein belongs to the D2-like receptor family. The other proteins in this family include D3 and D4. The D2 receptor is encoded by the gene DRD2. D2 receptor has two states: full active (D₂^HighR) and inactive (D₂^LowR) states. The receptor interchanges in these states when it is in complex with an agonist and antagonist, respectively.

The D2 receptor is highly expressed in the caudate, putamen, nucleus accumbens, ventral tegmental area, and substantia nigra. Moreover, its expression is very low in the septal region, amygdala, hippocampus, thalamus, cerebellum, and cerebral cortex. Furthermore, bromocriptine, cabergoline, aplinore, aripiprazole, armodafinil, etc. are some examples of D2 receptor agonists, while atypical antipsychotics, cinnarizine, chloroethylnorapomorphine, desmethoxyfallyprode, etc. are some examples of D2 receptor antagonists.

What are the Similarities Between D1 and D2 Receptors?

D1 and D2 Receptors are two main types of dopamine receptors.
Both receptors are proteins.
Both receptors are present in the vertebrate central nervous system (CNS).
They are highly implicated in vital functions in humans, such as memory, attention, and locomotion.
Both receptors have peculiar agonists and antagonists.

What is the Difference Between D1 and D2 Receptors?

The D1 receptor is a protein that regulates memory, attention, impulse control, renal function, and locomotion in humans, while the D2 receptor is a protein that regulates locomotion, attention, sleep, memory, and learning in humans. Thus, this is the key difference between D1 and D2 receptors. Furthermore, the D1 receptor is encoded by the DRD1 gene, while the D2 receptor is encoded by the DRD2 gene.

The below infographic presents the differences between D1 and D2 receptors in tabular form for side-by-side comparison.

Summary – D1 vs D2 Receptors

Dopamine receptors are receptors prominently present in the vertebrate central nervous system (CNS). D1 and D2 Receptors are two main types of dopamine receptors. Dopamine is the primary endogenous ligand for both dopamine receptors. The D1 receptor is a protein that regulates memory, attention, impulse control, renal function, and locomotion in humans, while the D2 receptor is a protein that regulates locomotion, attention, sleep, memory, and learning in humans. So, this summarizes the difference between D1 and D2 receptors.

Reference:

1. “Dopamine Receptor D1.” An Overview | ScienceDirect Topics.
2. “D2 Receptors in Psychopharmacology.” Psychopharmacology Institute.

Image Courtesy:

1. “Heroin 1 1” By A09231315 – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “TAAR1 Dopamine” By Seppi333 – Own work (CC BY-SA 3.0) via Commons Wikimedia