Dopaminergic cell groups, DA cell groups, or dopaminergic nuclei are collections of

neuron A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. N ...

s in the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all par ...

that synthesize the

neurotransmitter A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, any main body part or target cell, may be another neuron, but could also be a gland or muscle cell. Neuro ...

dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic compound, organic chemical of the catecholamine and phenethylamine families. Dopamine const ...

. In the 1960s,

dopaminergic neurons Dopaminergic cell groups, DA cell groups, or dopaminergic nuclei are collections of neurons in the central nervous system that synthesize the neurotransmitter dopamine. In the 1960s, dopaminergic neurons or ''dopamine neurons'' were first ident ...

or ''dopamine neurons'' were first identified and named by Annica Dahlström and Kjell Fuxe, who used

histochemical Histology, also known as microscopic anatomy or microanatomy, is the branch of biology which studies the microscopic anatomy of biological tissues. Histology is the microscopic counterpart to gross anatomy, which looks at larger structures vis ...

fluorescence Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...

. The subsequent discovery of genes encoding enzymes that synthesize dopamine, and transporters that incorporate dopamine into synaptic vesicles or reclaim it after synaptic release, enabled scientists to identify dopaminergic neurons by labeling gene or protein expression that is specific to these neurons. In the mammalian brain, dopaminergic neurons form a semi-continuous population extending from the midbrain through the forebrain, with eleven named collections or clusters among them.

Cell group A8

Group A8 is a small group of dopaminergic cells in rodents and primates. It is located in the

midbrain reticular formation The midbrain reticular formation (MRF), also known as reticular formation of midbrain, mesencephalic reticular formation, tegmental reticular formation, and formatio reticularis (tegmenti) mesencephali, is a structure in the midbrain consisting of ...

dorsolateral to the

substantia nigra The substantia nigra (SN) is a basal ganglia structure located in the midbrain that plays an important role in reward and movement. ''Substantia nigra'' is Latin for "black substance", reflecting the fact that parts of the substantia nigra app ...

at the level of the

red nucleus The red nucleus or nucleus ruber is a structure in the rostral midbrain involved in motor coordination. The red nucleus is pale pink, which is believed to be due to the presence of iron in at least two different forms: hemoglobin and ferritin. ...

and

caudally Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

. In the mouse it is identified with the retrorubral field as defined by classical stains.

Cell group A9

Group A9 is the most densely packed group of dopaminergic cells, and is located in the ventrolateral midbrain of rodents and primates. It is for the most part identical with the

pars compacta The pars compacta (SNpc) is a portion of the ''substantia nigra'', located in the midbrain. It is formed by dopaminergic neurons and located medial to the pars reticulata. Parkinson's disease is characterized by the death of dopaminergic neurons ...

of the substantia nigra as seen from the accumulation of neuromelanin pigment in the midbrain of healthy, adult humans.

Cell group A10

Group A10 is the largest group of dopaminergic cells in the

ventral Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. Th ...

midbrain

tegmentum The tegmentum (from Latin for "covering") is a general area within the brainstem. The tegmentum is the ventral part of the midbrain and the tectum is the dorsal part of the midbrain. It is located between the ventricular system and distinctive b ...

of rodents and primates. The cells are located for the most part in the

ventral tegmental area The ventral tegmental area (VTA) (tegmentum is Latin for ''covering''), also known as the ventral tegmental area of Tsai, or simply ventral tegmentum, is a group of neurons located close to the midline on the floor of the midbrain. The VTA is the ...

, the linear nucleus and, in primates, the part of central gray of the midbrain located between the left and right oculomotor nuclear complexes.

Cell group A11

Group A11 is a small group of dopaminergic cells located in the posterior

periventricular nucleus The periventricular nucleus is a thin sheet of small neurons located in the wall of the third ventricle, a composite structure of the hypothalamus. It functions in analgesia. It is located in the rostral, intermediate, and caudal regions of t ...

and the intermediate periventricular nucleus of the

hypothalamus The hypothalamus () is a part of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrine system via the pituitary gland. The hypothalamu ...

in the macaque. In the rat, small numbers of cells assigned to this group are also found in the posterior nucleus of hypothalamus, the supramammillary area and the reuniens nucleus. Dopaminergic cells in A11 may be important in the modulation of auditory processing.

Cell group A12

Group A12 is a small group of cells in the

arcuate nucleus The arcuate nucleus of the hypothalamus (also known as ARH, ARC, or infundibular nucleus) is an aggregation of neurons in the mediobasal hypothalamus, adjacent to the third ventricle and the median eminence. The arcuate nucleus includes several ...

of the hypothalamus in primates. In the rat a few cells belonging to this group are also seen in the anteroventral portion of the paraventricular nucleus of the hypothalamus.

Cell group A13

Group A13 is distributed in clusters that, in the primate, are ventral and medial to the

mammillothalamic tract The mammillothalamic tract (mammillothalamic fasciculus, thalamomammillary fasciculus, bundle of Vicq d’Azyr) arises from cells in both the medial and lateral nuclei of the mammillary body and by fibers that are directly continued from the forn ...

of the hypothalamus; a few extend into the reuniens nucleus of the

thalamus The thalamus (from Greek θάλαμος, "chamber") is a large mass of gray matter located in the dorsal part of the diencephalon (a division of the forebrain). Nerve fibers project out of the thalamus to the cerebral cortex in all directions, ...

. In the mouse, A13 is located ventral to the mammillothalamic tract of the thalamus in the zona incerta.

Cell group A14

Group A14 consists of a few cells observed in and near the preoptic periventricular nucleus of the primate. In the mouse, cells in the anterodorsal preoptic nucleus are assigned to this group.

Cell group A15

Group A15 exists in a few species, such as sheep, and immunoreactive for

tyrosine hydroxylase Tyrosine hydroxylase or tyrosine 3-monooxygenase is the enzyme responsible for catalyzing the conversion of the amino acid L-tyrosine to L-3,4-dihydroxyphenylalanine (L-DOPA). It does so using molecular oxygen (O2), as well as iron (Fe2+) and t ...

, a precursor of dopamine, in many other species including rodents and primates. It is located in ventral and dorsal components within the preoptic periventricular nucleus and adjacent parts of the anterior hypothalamic region. It is continuous caudally with the dopaminergic group A14.

Cell group A16

Group A16 is located in the

olfactory bulb The olfactory bulb (Latin: ''bulbus olfactorius'') is a grey matter, neural structure of the vertebrate forebrain involved in olfaction, the sense of odor, smell. It sends olfactory information to be further processed in the amygdala, the orbitof ...

of vertebrates, including rodents and primates.

Cell group Aaq

Group Aaq is a sparse group of cells located in the rostral half of the central gray of the midbrain in primates. It is more prominent in the squirrel monkey (Saimiri) than the macaque.

Telencephalic group

This group is a population of cells immunoreactive for dopamine and tyrosine hydroxylase that are broadly distributed in the rostral

forebrain In the anatomy of the brain of vertebrates, the forebrain or prosencephalon is the Anatomical terms of location#Directional terms, rostral (forward-most) portion of the brain. The forebrain (prosencephalon), the midbrain (mesencephalon), and hin ...

, including such structures as: substantia innominata, diagonal band,

olfactory tubercle The olfactory tubercle (OT), also known as the tuberculum olfactorium, is a multi-sensory processing center that is contained within the olfactory cortex and ventral striatum and plays a role in reward cognition. The OT has also been shown to ...

prepyriform area Prepyriform area (or prepiriform cortex) is a portion of the rhinencephalon consisting of paleocortex. Some sources state that it is part of the primary olfactory cortex The primary olfactory cortex (POC) is a portion of the cerebral cortex. ...

striatum The striatum, or corpus striatum (also called the striate nucleus), is a nucleus (a cluster of neurons) in the subcortical basal ganglia of the forebrain. The striatum is a critical component of the motor and reward systems; receives glutamate ...

(at levels rostral to the anterior

commissure A commissure () is the location at which two objects abut or are joined. The term is used especially in the fields of anatomy and biology. * The most common usage of the term refers to the brain's commissures, of which there are five. Such a commi ...

claustrum The claustrum (Latin, meaning "to close" or "to shut") is a thin, bilateral collection of neurons and supporting glial cells, that connects to cortical (e.g., the pre-frontal cortex) and subcortical regions (e.g., the thalamus) of the brain. It ...

, and deep cortical layers of all

gyri In neuroanatomy, a gyrus (pl. gyri) is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci (depressions or furrows; sg. ''sulcus''). Gyri and sulci create the folded appearance of the brain in humans and other ma ...

of the

frontal lobe The frontal lobe is the largest of the four major lobes of the brain in mammals, and is located at the front of each cerebral hemisphere (in front of the parietal lobe and the temporal lobe). It is parted from the parietal lobe by a groove betwe ...

rostral to the head of the caudate nucleus; the cells are also numerous in intervening

white matter White matter refers to areas of the central nervous system (CNS) that are mainly made up of myelinated axons, also called tracts. Long thought to be passive tissue, white matter affects learning and brain functions, modulating the distribution ...

, including the

external capsule The external capsule is a series of white matter fiber tracts in the brain. These fibers run between the most lateral (toward the side of the head) segment of the lentiform nucleus (more specifically the putamen) and the claustrum. The white matt ...

extreme capsule The extreme capsule (Latin: capsula extrema) is a series of nerve tracts between the claustrum and the insular cortex. It is also described as a thin capsule of white matter as association fibres. The extreme capsule is separated from the external ...

and frontal white matter. They are found in the rodent, the macaque and the human.

Footnotes

References

* * * * * * * * {{cite book, vauthors=Tillet Y, year=1994, chapter=9: Catecholaminergic neuronal systems in the diencephalon of mammals, title=Phylogeny and Development of Catecholamine Systems in the CNS of Vertebrates, veditors=((Smeets WJAJ)), Reiner A, publisher=University Press, location=Cambridge, England, oclc=29952121, isbn=978-0-5214-4251-0 Dopamine