Arcuate nucleus

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Arcuate nucleus
Arcuate nucleus is 'AR', at bottom center, in green.
Details
Part ofHypothalamus
Identifiers
Latinnucleus arcuatus hypothalami
MeSHD001111
NeuroNames395
NeuroLex IDbirnlex_1638
TA98A14.1.08.923
TA25726
FMA62329
Anatomical terms of neuroanatomy

The arcuate nucleus of the hypothalamus (also known as ARH,[1] ARC,[2] or infundibular nucleus[2][3]) is an aggregation of neurons in the mediobasal hypothalamus, adjacent to the third ventricle and the median eminence. The arcuate nucleus includes several important and diverse populations of neurons that help mediate different neuroendocrine and physiological functions, including neuroendocrine neurons, centrally projecting neurons, and astrocytes. The populations of neurons found in the arcuate nucleus are based on the hormones they secrete or interact with and are responsible for hypothalamic function, such as regulating hormones released from the pituitary gland or secreting their own hormones. Neurons in this region are also responsible for integrating information and providing inputs to other nuclei in the hypothalamus or inputs to areas outside this region of the brain. These neurons, generated from the ventral part of the periventricular epithelium during embryonic development, locate dorsally in the hypothalamus, becoming part of the ventromedial hypothalamic region.[1][2][4] The function of the arcuate nucleus relies on its diversity of neurons, but its central role is involved in homeostasis. The arcuate nucleus provides many physiological roles involved in feeding, metabolism, fertility, and cardiovascular regulation.[1][2][4][5]

Cell populations

Neuroendocrine neurons

Different groups of arcuate nucleus neuroendocrine neurons secrete various types or combinations of

polypeptide that is cleaved into MSH, ACTH, and β-endorphin and expressed in the arcuate nucleus.[1]

Groups of neuroendocrine neurons include:

  • TIDA neurons, or
    hyperprolactinemic) women experience oligomenorrhea or amenorrhea (infrequency or absence of menses).[6]
  • Kisspeptin/NKB neurons within the arcuate nucleus form synaptic inputs with TIDA neurons. These neurons express estrogen receptors and also coexpress neurokinin B in female rats.[7]
  • GHRH neurons help to control growth hormone (GH) secretion in conjunction with somatostatin and NPY.[8]
  • NPY/AgRP neurons and POMC/CART neurons make up two groups of neurons in the arcuate nucleus that are centrally involved in the neuroendocrine function of feeding. Medial neurons utilize NPY peptides as neurotransmitters to stimulate appetite, and lateral neurons utilize POMC/CART to inhibit appetite.[2] NPY and POMC/CART neurons are sensitive to peripheral hormones such as leptin and insulin.[4] POMC/CART neurons also secrete melanocyte-stimulating hormone, which suppresses appetite.[9][10]: 419 
  • GnRH neurons have also been found.[1][2] These neurons secrete GnRH and histamine.[2]
  • There are also groups of neurons expressing NKB and dynorphin that help to control reproduction.[2]

Centrally-projecting neurons

Other types of neurons have projection pathways from the arcuate nucleus to mediate different regions of the hypothalamus or to other regions outside of the hypothalamus.

lateral hypothalamic area (LHA).[1] Populations of neurons connect to the intermediate lobes of the pituitary gland, from the lateral division of the ARH to the neural and intermediate parts of the pituitary gland, and the caudal division of ARH to the median eminence.[2]

Groups of neurons that project elsewhere within the central nervous system include:

Other neurons

Other cell populations include:

  • A small population of neurons that sensitive to ghrelin. The role of this population is not known; many neurons in the arcuate nucleus express receptors for ghrelin, but these are thought to respond mainly to blood-borne ghrelin.[12][13]
  • The arcuate nucleus also contains a population of specialized
    tanycytes
    .
  • Astrocytes in the arcuate nucleus hold high capacity glucose transporters that function as nutrient sensors for appetite controlling neurons[2]
  • The diverse and specialized collections of neurons reside within a special compartment with
    glial cells and have their own network of capillaries and a membrane of tanycytes that help create a blood brain barrier.[2] Circulating or molecules such as hormones travel in the blood and can directly affect these neurons and their plasticity as evidence by adult neurogenesis.[2]

References

Footnotes