User:Merchantofvenice9/sandbox

I will be adding to the arcuate nucleus (hypothalamus) wikipedia page by adding information about the arcuate nucleus in terms of its anatomy, specialized features, and its function or physiological role(s). I am hoping to find the citations for the information already posted. This is the bibiolography of resources that I have so far:

Bouret,S.G., Draper, S.J., Simerly, R.B. (2004), Formation of Projection Pathways from Arcuate Nucleus of the Hypothalalmus to Hypothalamic Regions implicated in the neural control of feeding behavior in Mice. The Journal of Neuroscience. 24(11):2797–280

Coppari R., Ichinose, M., Lee, C., Pullen, A., Kenny, C. McGovern, R., Tang, V., Lui S. Ludwig, T. Chua, S. Lowell, B., Elmquist J. (2005) The hypothalamic arcuate nucleus: A key site for mediating leptin’s effects on glucose homeostasis and locomotor activity. Cell Metabolism.

Dudás, B. (2013). The Human Hypothalamus: Anatomy, Functions and Disorders. New York: Nova Science Publishers, Inc.

Dampney, R. A. L. (2011), Arcuate nucleus – a gateway for insulin's action on sympathetic activity. The Journal of Physiology, 589: 2109–2110.

Sainsbury, A. and Zhang L. (2010). Role of the arcuate nucleus of the hypothalamus in regulation of body weight during energy deficit. Molecular and Cellular Endocrinology 316: 109–119

Sapru. Hreday. 2013. Role of the hypothalamic arcuate nucleus in cardiovascular regulation. Autonomic Neuroscience: Basic and Clinical 175: 38–50.

Note ***I will be now adding to the arcuate nucleus in the hypothalamus wikipedia article not the arcuate nucleus in the medulla

Here's my outline: There's a lot of information so I am planning on condensing this information for my lead in section.

Arcuate Nucleus

The arcuate nucleus is a group of neurons in a specific region of the hypothalamus that help to mediate different neuroendocrine and physiological functions

·     Definition

o  Known as ARH or ARC

o  A collection of neurons in the central nervous system that form synaptic connections with other neurons in the hypothalamus or outside of the hypothalamus.

o  Have different neurons with different receptors that interact with circulating hormones

o  Neurons generated from the ventral part of the periventricular neuroepithelium during embryonic development

o  Groups of neurons that utilize different combinations of neurotransmitters such as

§ Neuropeptide Y  (NPY)

§ Propiomelanocortin (POMC)

§ Kisseptin/neurokinin b/dynorphin

§ dopamine

§ Substance p

§ Growth hormone releasing hormone/somatostatin

·     Location (found in both the hypothalamus and medulla)

o  Component of the forebrain pathway

o  Located in proximity to the capillaries of the median eminence, part of the hypothalamus that is release regulatory hormones

o  Ventromedial hypothalamus includes the ARC (arcuate nucleus)  and Ventral medial nucleus (VMN) (6)

·     Function

o  Nervous system impact

§ Provides hypothalamic function

§ Neuroendocrine functions

·     Ex. relays leptin signals to other parts of the hypothalamus

·     Contains neuroendrocrine neurons that release hormones and or regulate those from the pituitary gland

·     Function

§ This collection of neurons process information received from the synapses of other neurons via synaptic communication

·     Integrates periphery signals from nervous system

·     Provide inputs to PV zone

§ Circulating molecules and hormones have effects on the arcuate nucleus

·     Hormones such as leptin, insulin, ghrelin influence the function of ARC neurons

o  Steroid hormones such as estrogen bind to both neuron and astrocytes in the ARH which influences appetite and control of reproductive hormones

o  Regulates secretion of Lutenizing hormone (LH) which influences activity of gonadotropin releasing hormone neurons and steroid production

o  Central role in circuits involved in homeostasis

§ Regulates food intake, energy expenditure, body weight

·     Damage to ARH

§ Results in stunted growth, obesity, reduced gonadotropin secretion and sterility

§ Glutamate lesions to ARC have shown that neurons are immunoreactive for the enzyme tyrosine hydroxylase

§ Abnormalities in ARH functioning can involve eating disorders such as anorexia nervosa and obesity syndrome

§ Hypoglycemia causes the DNA damage in ARC cells and in the dorsal medulla showing that the ARC is very reactive to blood glucose than most brain regions (3)

§ Study suggests that symptoms of diabetes mellitus may also

come from abnormalities in the ARC

·     referring to general insensitivity of peripheral tissues to insulin

§ Neuronal loss in this area is involved in obesity syndrome

§ Lesions to this area can result in leptin insensitivity

·     Anatomy

o  Arcuate nucleus from the dorsal part of the hypothalamus forms a special compartment which contained specialized, diverse collection of neurons and glial cells (3)

o  Collection of heterogeneous neurons dorsal to the median eminence

o  Boundaries of the arcuate nucleus are less defined in humans

·     Projection Pathways***

o  Projections of arcuate nucleus neurons are not mature until a few week after birth in animals

o  Neurons project and extend a great distance from the arcuate nucleus to the median eminence

o  Others project into other hypothalamic sites, which influence the release of hormones from the pituitary gland

o  Receive many direct synaptic inputs from nearby hypothalamic nuclei or extra hypothalamic sites such as the amygdala, hippocampus, Entorhinal cortex

o  Nuclei are similar to other CNS nuclei in that they process sensory information and relay this information to other collection of neurons

o  Projections mediate different regions the hypothalamus

o  Have intrahypothalamic projections as part of neuroendocrine circuitry

o  Have neural projections going into the following areas which are points in neural pathway regulating feeding behavior:

§ the paraventricular nucleus of the hypothalamus (PVH)

§ dorsomedial hypothalamic nucleus (DMH)

§ Lateral hypothalamic area (LHA)

·     Specialized features

o  Has it own network of capillaries within itself and a permeable barrier composed of ependymal cells called tanycytes that form a blood brain barrier

o  Affected by circulating molecules that travel in the blood

o  Studies have shown signs of plasticity within the arcuate nucleus as evidenced by adult neurogenesis

§ Leptin affects excitatory and inhibitory synapses of ARC neurons and influences their neural development

o  What makes it unique is that the arcuate nucleus also processes blood-borne molecules which usually have direct access to the ARH

·     Groups of neurons

o  Medial neurons: utilize NPY peptide and neurotransmitters to stimulate appetite

§ NPY neurons show anorexigenic functions: results in decrease in feeding and increase in energy expenditure

o  Lateral neurons: utilize POMC/CART as neurotransmitters to inhibit appetite

o  NPY and POMC/CART neurons are regulated by peripheral hormones such as insulin and leptin

o  Neurons that’s express neurokinin b/ dynorphin which helps to control reproduction

o  Neurons expressing dopamine regulate prolactin secretion

o  Astrocytes in the arcuate nucleus have high capacity glucose transporters and function as nutrient sensors that function as appetite controlling neurons (3)

§ Activation required for normal puberty in rats (3)

§ Astrocytes have GLUT2 transporters for glucose sensing apparatus

o  Glucose sensing neurons are involved in sympathetic excitation (6)

o  Agouti-related peptide neurons found in ARC

o  Contains leptin responsive neurons

o  Arcuate nucleus contains a large number of gonadotropin releasing neurons

o  Feeding regulatory neurons activate oxytocin containing neurons of the periventricular nucleus (PVN) which projects to the nucleus of tractus solitarus in the medulla oblongata (3)

o  3 main populations of neurons connecting ARC to pituitary gland:

§  project into the intermediate lobes of the pituitary lobe influencing MSH secretion

§ one to the lateral division neural and intermediate parts of the pituitary gland

§  the caudal division projects into the median eminence to regulate prolactin secretion

Physiological roles:

o  Effects on obesity, fertility, metabolic alterations

o  ARC neurons directly modify insulin secretion, shivering thermogenesis and insulin stimulated fat deposition by altering the parasympathetic nervous system

o  Neurons decrease food intake, stimulates gonadotropin secretion, promoting puberty and suppressing lipogenesis

o  Ghrelin –stimulates growth hormone releasing neurons of the ARC regulating the production of growth hormone

o  Estrogen- many ARC neurons have receptors for steroid hormones such as estrogen and progesterone

o  Impact of estrogen on reducing feeding behavior, increasing the activity of POMC neurons, and decreasing activity in NPY secreting neurons

o  Also affects ARC neurons that secrete kisseptin and gonadotropin

o  Insulin action in glucose homeostasis and sympathetic activity

o  Neurons influence insulin sensitivity and glucose metabolism in the autonomic nervous system

o  Regulates appetite and regulates overall body lipid deposits

o  Lipid effects on the ARC include lipid metabolism within the ARC

o  The intraventricular fusion of oleic acid decreases food intake

o  Secretion of gonadotropins and metabolism histamine

o  Sensitive to feeding related hormones and reacts to changes in glucose availability

o  Regulation of cardiovascular functions

o  Chemical stimulation of ARC has shown increase in activity in other regions

o  For example an increase in blood pressure following stimulation of the Arc

o  Depressor and presser responses can be produced by stimulation of the ARC

o  If you stimulate the ARC you can activate  NPY, GABA and beta-nedoprhin neurons n the PVN (periventricular nucleus)

o  Mediates Leptin action on energy homeostasis

o  Leptin is peptide needed to regulate normal body weight and glucose homeostasis

o  Leptin inhibits NPY secreting neurons in arcuate nucleus

o  ARC is an important site of the hypothalamus that mediates the effects of leptin

o  Data has suggested that leptin signaling in the arcuate nucleus is enough to mediate its action on body weight homeostasis

o  Signaling of leptin in ARC has shown regulation of body weigh such as the reduction of body weight

o  Leptin decreases NPY neurons in ARC which stimulates feeding response

o  Arc neurons mediate leptin effects

o  Restoring leptin receptors in the arcuate nucleus improves glucose homeostasis and insulinemia can be greatly reduced

o  Leptin effects on ARC has also been known to affect fertility

o  When mice ARC was injected with leptin it significantly increased locomotor activity compared to mice with leptin

o  Restoring the physiological signaling of leptin can prevent obesity as was observed with leptin-deficient mice and has also been shown to help mediate normal blood glucose levels and improve hyperinsulinemia

o  If insulin receptors are disrupted in the ARC this results in hyperphagia (abnormal increased appetite for food)

§ It also increases the expression of NPY peptide and can cause insulin resistance in the liver

o  Energy deficits

o  Energy deficit is an increase in food intake, reduced physical activity and decrease in metabolic regulation

o  At least in part, some hypothalamic features with the Arcuate nucleus mediate energy conserving adaptations during energy deficit

o  Hypothalamic regulators such as the NPY and AgRp (agouti related peptide) are involved in regulating food intake, energy expenditure and physical activity

o  The arcuate nucleus interacts with the PVN (periventricular nucleus) as part of a energy conserving adaptation

o  In the arcuate nucleus, energy restriction upregulates the expression of peptides NPY and AgRP and down regulates alpha-MSH or POMC/CART expression ---NPY involved in increasing food intake and POMC is the opposite

Plan: The article for arcuate nucleus of the hypothalamus lacks citations for the information provided. It goes into the groups of neurons found in this area, however it does not discuss the physiological roles or effects from the arcuate nucleus

-not sure if it would be worth it to look at some the pathways of the arcuate nuclei projections

Expanded Draft:

The arcuate nucleus (or infundibular nucleus[1]) is an aggregation of neurons in the mediobasal hypothalamus, adjacent to the third ventricle and the median eminence. The arcuate nucleus includes several important populations of neurons, including: neuroendocrine neurons, centrally projecting neurons, and others. (copied from Wikipedia article)

Background

The arcuate nucleus of the hypothalamus, also known as ARH, ARC, or the infindibular nucleus is a diverse group of neurons that help mediate different neuroendocrine and physiological functions. 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. The populations of neurons found in the arcuate nucleus are based off of what 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. Arcuate nucleus neurons utilize different combinations of neurotransmitters such as neuropeptide Y (NPY), propiomelanocortin (POMC), kisspeptin, dopamine, substance p, growth hormone releasing hormone (GhRH), and somatostatin. Other types of neurons have projection pathways reaching great distances from the arcuate nucleus to mediate different regions of the hypothalamus or to other regions outside of the hypothalamus. The arcuate nucleus provides many physiological roles involved in feeding, metabolism, fertility, and cardiovascular regulation. Lesions or damage to ARH functioning can lead to stunted growth, obesity, eating disorders, reduced gonadotropin secretion and sterility, as well as leptin insensitivity.

Anatomy, Location, and Specialized Features

The arcuate nucleus is a component of the forebrain pathway that is in proximity to the median eminence and ventral medial nucleus (VMN). The boundaries of this structure are less defined in humans than they are in rats. 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. Circulating or molecules such as hormones travel in the blood and can directly affect these neurons and their plasticity as evidence by adult neurogenesis. For example, leptin affects the excitatory and inhibitory synapses of ARH neurons, influencing their neuronal development.

Function

The function of the arcuate nucleus relies on its diversity of neurons. Some groups of neurons work as neuroendocrine neurons that release hormones or regulate hormones released from the pituitary gland, whereas other groups of neurons act as projection pathways for synaptic communication and integrate periphery signals from the nervous system. The Arcuate nuclei are similar to nuclei found in the central nervous system in that they process sensory information and relay them to other collections of neurons. These neurons are involved in mediating different regions of the hypothalamus. For example, arcuate nucleus neurons provide inputs to the periventricular zone (PVZ).

Groups of neurons

The arcuate nucleus contains two groups of neurons involved in the neuroendocrine function of feeding. Medial neurons utilize NPY peptide and neurotransmitters to stimulate appetite, and lateral neurons utilize POMC/CART to inhibit appetite. NPY and POMC/CART neurons are sensitive to peripheral hormones leptin and insulin. There are also groups of neurons expressing neurokinin b/ dynorphin that help to control reproduction, neurons expressing dopamine that are involved in prolactin secretion. Gonadotropin releasing neurons and Agouti-related peptide secreting neurons have also been found. Astrocytes in the arcuate nucleus hold high capacity glucose transporters that function as nutrient sensors for appetite controlling neurons discussed above. 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.

Projection Neurons

Projections of neurons extend a long distance from the arcuate nucleus to the median eminence to influence the release of hormones from the pituitary gland. Neurons of the Arcuate nucleus have intrahypothalamic projections for neuroendrocine circuitry which includes neural projections that influence feeding behavior in the paraventricular nucleus of the hypothalamus (PVH), the dorsomedial hypothalamic nucleus (DMH, and the lateral hypothalamic area (LHA. Feeding regulatory neurons also activate oxytocin-containing neurons of the periventricular nucleus (PVN), which projects to nucleus of tractus solitarus in the medulla oblongata. Others receive direct synaptic inputs from extra hypothalamic sites projecting into the amygdala, the hippocampus, and the Entorhinal cortex.

Physiological roles and Neuroendocrine Function

The central role of arcuate nucleus is involved in homeostasis. Chemical stimulation of the arcuate nucleus has been shown to increase activity in other regions. Signaling effects on arcuate nucleus neurons, especially with leptin, exhibit physiological roles that help with homeostasis, mainly in the regulation of food intake, energy expenditure and body weight. Projection neurons connecting the arcuate nucleus to different parts of the pituitary gland influence MSH secretion, prolactin secretion and other hormonal secretions. Neurons of the arcuate nucleus directly modify insulin secretion, shivering thermogenesis and insulin stimulated fat deposition by altering the parasympathetic nervous system (citation needed). Neurons in the ARC also secrete gonadotropins and metabolic histamine and regulate the secretion of lutenizing hormone (LH), which influences the activity of gonadotropin releasing hormone and steroid production. Steroid hormones such as estrogen bind to both neurons and astrocytes on the ARH to influence appetite and control production of reproductive hormones. Estrogen can reduce feeding behavior by increasing the activity of POMC neurons and decreasing the activity of NPY neurons and is known to also affects neurons secreting kisseptin and gonadotropin. Ghrelin stimulates the growth hormone releasing neurons of the arcuate nucleus that regulate the production of growth hormone.

One important example of neuroendocrine functioning ARH neurons includes relaying leptin signals to other parts of the hypothalamus. The ARH may also have an indirect role in cardiovascular regulation. Upon stimulation of the ARH, NPY, GABA and beta-endorphin neurons in the periventricular nucleus (PVN) are activated and the production of pressor and depressor responses have been observed.

ARH regulation of metabolism (Energy homeostasis)

The arcuate nucleus is an important site of the hypothalamus that mediates leptin action on energy homeostasis. Leptin signaling in the arcuate nucleus is significant in acting on body weight homeostasis, helping to reduce body weight. This peptide decreases NPY neuronal stimulation, which normally stimulates a feeding response. ARH neurons are sensitive to feeding related hormones and react to changes in glucose availability. If insulin receptors are disrupted in ARH then hyperphagia can result and the up-regulated expression of NPY peptides can cause insulin resistance in the liver. Leptin effects on ARH have been known affect fertility and locomotor activity in mice compared to mice that are leptin deficient. Restoring the normal signaling of leptin can prevent obesity as observed with leptin-deficient mice and helps mediate normal blood glucose levels and improve hyperinsulinemia conditions. Hypothalamic features of the arcuate nucleus mediate energy conserving adaptations during energy deficit by interacting with the periventricular zone. Energy deficit is known as an increase in food intake, a reduction in physical activity and a decrease in metabolic regulation. Hypothalamic regulators NPY and AgRp (agouti related peptide) act on neurons in the arcuate nucleus to regulate food intake, energy expenditure, and physical activity. As energy restriction up regulates the expression of MYPY and AgRp peptides, it down regulates the POMC/CART expression, involved in decreasing food intake. Neurons of the ARH also regulate overall body lipid deposits as intraventricular fusion of oleic acid decreases food intake (citation needed).

Editing Wikipedia article sections:

Section 1:

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 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 off of what 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.

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.

Section 2:

Different groups of arcuate nucleus neuroendocrine neurons secrete various types or combinations of neurotransmitters, such as neuropeptide Y (NPY), Agouti-related peptid e (Agrp) propiomelanocortin (POMC), kisspeptin, dopamine, substance p, growth hormone releasing hormone (GhRH), and somatostatin.

(Copied from wikipedia article and added to)

Groups of neuroendocrine neurons include:
 * the tuberoinfundibular pathway: neurons with nerve endings in the median eminence release dopamine into the hypophysial portal blood. These are sometimes called the "tuberoinfundibular dopamine" (TIDA) neurons. In lactating females, TIDA neurons are inhibited by the stimulus of suckling. Dopamine released from their nerve endings at the median eminence is transported to the anterior pituitary gland, where it regulates the secretion of prolactin; dopamine inhibits prolactin secretion, so when the TIDA neurons are inhibited, there is increased secretion of prolactin, which stimulates lactogenesis (milk production). Prolactin acts in a short-loop negative feedback manner to decrease its levels by stimulating the release of dopamine. Dopaminergic neurons of the arcuate also inhibit the release of gonadotropin-releasing hormone, explaining in part why lactating (or otherwise hyperprolactinemic) women experience oligomenorrhea or amenorrhea (infrequency or absence of menses).
 * Neuroendocrine neurons, mainly in the ventrolateral part of the nucleus, make growth hormone-releasing hormone (GHRH). Like the TIDA neurons, these neurons have nerve endings in the median eminence. GHRH released into the hypophysial portal blood is transported to the anterior pituitary gland, where it regulates the secretion of growth hormone; GHRH stimulates growth hormone secretion. These neurons are inhibited by somatostatin. The reciprocal relationship between the electrical activity of GHRH neurons and somatostatin neurons leads to pulsatile secretion of growth hormone, a pattern of secretion that is important for its biological effectiveness.
 * The arcuate nucleus contains two groups of neurons involved in the neuroendocrine function of feeding. Medial neurons utilize NPY peptide and neurotransmitters to stimulate appetite, and lateral neurons utilize POMC/CART to inhibit appetite. NPY and POMC/CART neurons are sensitive to peripheral hormones leptin and insulin.
 * Gonadotropin releasing neurons and Agouti-related peptide secreting neurons have also been found. Neurons in the ARC also secrete gonadotropins and metabolic histamine and regulate the secretion of lutenizing hormone (LH), which influences the activity of gonadotropin releasing hormone and steroid production.
 * There are also groups of neurons expressing neurokinin b/ dynorphin that help to control reproduction.

Section 3:

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. Projections of these neurons extend a long distance from the arcuate nucleus to the median eminence to influence the release of hormones from the pituitary gland. Neurons of the Arcuate nucleus have intrahypothalamic projections for neuroendrocine circuitry which includes neural projections that influence feeding behavior in the paraventricular nucleus of the hypothalamus (PVH), the dorsomedial hypothalamic nucleus (DMH, and the lateral hypothalamic area (LHA).
 * Centrally projecting neurons that contain neuropeptide Y (NPY), agouti-related protein (AGRP), and the inhibitory neurotransmitter GABA. These neurons, in the most ventromedial part of the nucleus, project strongly to the lateral hypothalamus and to the paraventricular nucleus of the hypothalamus, and are important in the regulation of appetite. When activated, these neurons can produce ravenous eating. These neurons are inhibited by leptin, insulin, and peptide YY and activated by ghrelin.
 * Centrally projecting neurons that contain peptide products of pro-opiomelanocortin (POMC), and cocaine- and amphetamine-regulated transcript (CART). These neurons have widespread projections to many brain areas, including to all nuclei in the hypothalamus. These cells are important in the regulation of appetite, and, when activated, they inhibit feeding. These neurons are activated by circulating concentrations of leptin and insulin, and they are directly innervated and inhibited by the NPY neurons.[10] POMC neurons that project to the medial preoptic nucleus are also involved in the regulation of sexual behavior in both males and females. The expression of POMC is regulated by gonadal steroids. The release of a POMC product, beta-endorphin is regulated by NPY.
 * Centrally projecting neurons that make somatostatin; the neurosecretory somatostatin neurons that regulate growth hormone secretion are a different population, located in the periventricular nucleus.
 * Feeding regulatory neurons also activate oxytocin-containing neurons of the periventricular nucleus (PVN), which projects to nucleus of tractus solitarus in the medulla oblongata.
 * Others receive direct synaptic inputs from extra hypothalamic sites projecting into the amygdala, the hippocampus, and the Entorhinal cortex.

Section 4: (Other)

Astrocytes in the arcuate nucleus hold high capacity glucose transporters that function as nutrient sensors for appetite controlling neurons discussed above. 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.

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. Circulating or molecules such as hormones travel in the blood and can directly affect these neurons and their plasticity as evidence by adult neurogenesis.

TIDA Neurons are Tuberofundibular dopaminergic neurons that regulate the secretion of prolactin from the pituitary gland and release GABA neurotransmitter. Are though to be involved in controlling prolactin (PRL) secretion by releasing dopamine

Kisseptin/NKB neurons within the arcuate nucleus form synaptic inputs with TIDA neurons. These neurons express estrogen receptors and also coexpress neurokinin B in rats


 * Those in the tuberoinfundibular pathway: neurons with nerve endings in the median eminence release dopamine into the hypophysial portal blood. These are sometimes called the "tuberoinfundibular dopamine" (TIDA) neurons. In lactating females, TIDA neurons are inhibited by the stimulus of suckling. Dopamine released from their nerve endings at the median eminence is transported to the anterior pituitary gland, where it regulates the secretion of prolactin; dopamine inhibits prolactin secretion, so when the TIDA neurons are inhibited, there is increased secretion of prolactin, which stimulates lactogenesis (milk production). Prolactin acts in a short-loop negative feedback manner to decrease its levels by stimulating the release of dopamine. Dopaminergic neurons of the arcuate also inhibit the release of gonadotropin-releasing hormone, explaining in part why lactating (or otherwise hyperprolactinemic) women experience oligomenorrhea or amenorrhea (infrequency or absence of menses).