What Are Dopamine Receptors?

The dopamine receptor is a receptor located in the body that functions through its corresponding membrane receptor. Dopamine receptors are a family of G protein-coupled receptors composed of seven transmembrane regions. Five dopamine receptors (DA2R) have been isolated.

Dopamine receptor

Five dopamine receptors (DA2R) have been isolated. According to their biochemical and pharmacological properties, they can be divided into D1 and D2 receptors. D1 receptors include D1 and D5 receptors (also known as D1A and D1B receptors in rats). D2 receptors include D2, D3, and D4 receptors. The C-terminus of both receptors contains

There are five dopamine receptors found today, D1, D2, D3, D4, and D5. Among them, D1, D5 are D1-like receptors, which increase cAMP levels in cells after activation, and D2, D3, and D4 are D2-like receptors. Reduces intracellular cAMP levels after activation.

Before the lack of specific ligands for each dopamine receptor subtype, in situ hybridization methods were widely used to study the distribution of dopamine receptor mRNAs in the brain. D1 and D2 receptor genes are widely expressed in the brain. D12R is mainly expressed in the caudate nucleus (CPu), the nucleus accumbens (Acb), the optic tract (OT), the cerebral cortex (Cx), and the amygdala. In addition, the D1 receptor is also detected in Calleja Island and the hypothalamus Here. Although D1 ligand was found to bind to the substantia nigra, no mRNA was detected. This result suggests that D12R is transported to the substantia nigra through the striatum nigra bundles after striatum synthesis. Compared with D12R and D12R, the expression is limited, and it is only expressed in the hippocampus, lateral papillary nucleus and hypothalamic nucleus. D22R mRNA is mainly expressed in CPu, OT and Acb of the brain. It is also expressed in the substantia nigra and ventral tegmental area (VTA). These areas emit dopamine fibers, suggesting that D22R has presynaptic localization. In contrast, D1-like receptors have only extensive post-synaptic localization. Analysis of the mRNAs of the two subtypes of the D2-like receptor revealed that D2L was most abundantly expressed. Outside the brain, D22R mRNA is also localized to the retina, kidney, vascular system, and pituitary. The mRNA distribution of rat brain D32R is limited to Callija islands, septum nuclei, hypothalamus and thalamus, and certain regions in the cerebellum. D32R is also distributed in the dense substantia nigra, suggesting that it also has presynaptic localization. D42R mRNA is highly expressed in the prefrontal cortex, amygdala, olfactory bulb, hippocampus, thalamus and midbrain.

Dopamine receptor subtype-specific antibodies can be used for cellular and subcellular localization in different brain regions. D1 and D5 receptors are co-expressed in the prefrontal cortex, premotor regions, cingulate and entorhinal cortex, hippocampal and dentate gyrus pyramidal cells. Electron microscopy confirmed the presence of D1 and D5 receptors in the prefrontal cortex, pre-synaptic and post-synaptic distributions in the hippocampus, with post-synaptic distribution more common. Ultrastructural analysis revealed that D1 and D5 receptors are distributed differently in human pyramidal cells, D1 receptors are concentrated in dendritic spines, and D5 receptors are concentrated in dendritic axes. In the olfactory bulb, the D1 receptor is limited to the inner granular layer and the inner sublayer; in the amygdala, it is limited to the mesial and lateral basal nucleus. In the caudate nucleus, D1 and D5 receptors are mostly located in medium-sized GABAergic neurons. D5 receptors are also present in large cholinergic intermediate neurons. Ultrastructural analysis found that D1 receptors are present in the asymmetric synaptic post-synaptic dendritic spines, D1 and D5 receptors are located on the post-synaptic dendrites characteristic of small synapses at the dopamine terminal, and pre-synaptic The D1 and D5 receptors are located on axons that form asymmetric synapses.

The D1 receptor has been identified in the foot core and the substantia nigra reticulum, and no D5 receptor has been detected in these regions. This result suggests that if the D1 and D5 receptors co-exist in the caudate nucleus with multiple spiny neurons, only the D1 receptors will be transferred to the striatum target region terminal. Although the D1 and D5 receptors have similar pharmacological properties, different cellular and subcellular localizations suggest that they may be functionally different. Immunohistochemical methods using specific antibodies showed that D2 receptors are present in the multispinous neurons in the striatum, and are more densely distributed in the spinous processes and spines than in the soma. Coexistence with the D1 receptor is very rare.

D2 immune response terminals form more symmetrical synapses than asymmetric synapses. D2 receptors exist in the nucleus and dendrites of the dense substantia nigra. Compared with other striatum projections, D2 receptors are more concentrated in the outer part of the pale globus. The D2 receptor immunopositive reaction can also be seen in the granular layer and inner layer of the olfactory bulb and the amygdala. Immunohistochemistry and electron microscopy revealed that D4 receptors exist in pyramidal and non-pyramidal neurons in the cerebral cortex and hippocampus, and they have been confirmed to be GABAergic intermediate neurons. In the cerebral cortex and hippocampus, D4 receptors regulate GABA transmission. D4 receptors have also been found in GABAergic neurons in the paleosphere segment, the nigro reticulum, and the thalamic reticulum.