Dopaminergic Cell Groups
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Dopaminergic cell groups, DA cell groups, or dopaminergic nuclei are collections of
neuron A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...
s in the
central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain, spinal cord and retina. The CNS is so named because the brain integrates the received information and coordinates and influences the activity o ...
that synthesize the
neurotransmitter A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a Chemical synapse, synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell. Neurotra ...
dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. It is an amine synthesized ...
. In the 1960s, dopaminergic neurons or ''dopamine neurons'' were first identified and named by Annica Dahlström and Kjell Fuxe, who used histochemical
fluorescence Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with colore ...
. 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 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 a ...
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 describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provi ...
. 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, SNc) is one of two subdivisions of the ''substantia nigra'' of the midbrain (the other being the pars reticulata); it is situated medial to the ''pars reticulata''. It is formed by dopaminergic neurons. It projects to th ...
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 describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
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 th ...
, 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 and the intermediate periventricular nucleus of the
hypothalamus The hypothalamus (: hypothalami; ) is a small part of the vertebrate brain that contains a number of nucleus (neuroanatomy), nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrin ...
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 (ARH), or ARC, is also known as the infundibular nucleus to distinguish it from the arcuate nucleus of the medulla oblongata in the brainstem. The arcuate nucleus is an aggregation of neurons in the medio ...
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 of the hypothalamus; a few extend into the reuniens nucleus of the
thalamus The thalamus (: thalami; from Greek language, Greek Wikt:θάλαμος, θάλαμος, "chamber") is a large mass of gray matter on the lateral wall of the third ventricle forming the wikt:dorsal, dorsal part of the diencephalon (a division of ...
. 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 ...
, 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 neural structure of the vertebrate forebrain involved in olfaction, the sense of smell. It sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex (OF ...
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 rostral (forward-most) portion of the brain. The forebrain controls body temperature, reproductive functions, eating, sleeping, and the display of emotions. Ve ...
, including such structures as: substantia innominata, diagonal band, olfactory tubercle, prepyriform area,
striatum The striatum (: striata) or corpus striatum is a cluster of interconnected nuclei that make up the largest structure of the subcortical basal ganglia. The striatum is a critical component of the motor and reward systems; receives glutamat ...
(at levels rostral to the anterior
commissure A commissure () is the location at which two objects wikt:abut#Verb, 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 at ...
),
claustrum The claustrum (Latin, meaning "to close" or "to shut") is a thin sheet of neurons and supporting glial cells in the brain, that connects to the cerebral cortex and subcortical regions including the amygdala, hippocampus and thalamus. It is locate ...
, and deep cortical layers of all
gyri In neuroanatomy, a gyrus (: gyri) is a ridge on the cerebral cortex. It is generally surrounded by one or more sulcus (neuroanatomy), sulci (depressions or furrows; : sulcus). Gyri and sulci create the folded appearance of the brain in huma ...
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 Sulcus (neur ...
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 that are mainly made up of myelinated axons, also called Nerve tract, tracts. Long thought to be passive tissue, white matter affects learning and brain functions, modulating the distr ...
, 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 and frontal white matter. They are found in the rodent, the macaque and the human.


See also

*
Dopaminergic pathways Dopaminergic pathways (dopamine pathways, dopaminergic projections) in the human brain are involved in both physiological and behavioral processes including movement, cognition, executive functions, reward, motivation, and neuroendocrine contro ...
* History of catecholamine research


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 WJ, Reiner A, publisher=University Press, location=Cambridge, England, oclc=29952121, isbn=978-0-5214-4251-0 Dopamine