| Paraventricular nucleus of hypothalamus | |
|---|---|
 Human paraventricular nucleus (PVN) in this coronal section is indicated by the shaded area. Dots representvasopressin (AVP) neurons (also seen in thesupraoptic nucleus, SON). The medial surface is the 3rd ventricle (3V). | |
 The paraventricular hypothalamus of the mouse brain | |
| Details | |
| Identifiers | |
| Latin | nucleus paraventricularis hypothalami |
| MeSH | D010286 |
| NeuroNames | 387 |
| NeuroLex ID | birnlex_1407 |
| TA98 | A14.1.08.909 |
| TA2 | 5722 |
| FMA | 62320 |
| Anatomical terms of neuroanatomy | |
Theparaventricular nucleus (PVN) is anucleus in thehypothalamus, located next to thethird ventricle. Many of itsneurons project to theposterior pituitary where they secreteoxytocin, and a smaller amount ofvasopressin. Other secretions arecorticotropin-releasing hormone (CRH) andthyrotropin-releasing hormone (TRH).[1] CRH and TRH are secreted into thehypophyseal portal system, and target effector endocrine cells in theanterior pituitary. Dysfunctions of the PVN can causehypersomnia in mice.[2] In humans, the dysfunction of the PVN and the other nuclei around it can lead todrowsiness for up to 20 hours per day.[3] The PVN is thought to mediate many diverse functions through differenthormones, includingosmoregulation,appetite,wakefulness, and the response of the body tostress.[4][5]
The paraventricular nucleus lies adjacent to thethird ventricle. It lies within the periventricular zone and is not to be confused with theperiventricular nucleus, which occupies a more medial position, beneath thethird ventricle. The PVN is highly vascularised and is protected by theblood–brain barrier, although itsneuroendocrine cells extend to sites (in themedian eminence and in theposterior pituitary) beyond the blood–brain barrier.[citation needed] PVN is accounting for only about 1% of the brain volume.In the rat, the PVN consists of approximately 100,000 neurons located in a volume of about 0.5 cubic millimetre.[6]
The PVN containsmagnocellular neurosecretory cells whoseaxons extend into theposterior pituitary,parvocellular neurosecretory cells that project to themedian eminence, ultimately signalling to theanterior pituitary, and several populations of other cells that project to many different brain regions including parvocellular preautonomic cells that project to thebrainstem andspinal cord.[citation needed]
Themagnocellular cells in the PVN elaborate and secrete twopeptide hormones:oxytocin andvasopressin.
These hormones are packaged into large vesicles, which are then transported down theunmyelinated axons of the cells and released from neurosecretory nerve terminals residing in the posterior pituitary gland.[citation needed]
Similar magnocellular neurons are found in thesupraoptic nucleus which also secrete vasopressin and a smaller amount of oxytocin.[citation needed]
The axons of theparvocellular neurosecretory neurons of the PVN project to the median eminence, a neurohemal organ at the base of the brain, where their neurosecretory nerve terminals release their hormones at the primary capillary plexus of thehypophyseal portal system. The median eminence contains fiber terminals from many hypothalamic neuroendocrine neurons, secreting different neurotransmitters or neuropeptides, including vasopressin, corticotropin-releasing hormone (CRH), thyrotropin-releasing hormone (TRH), gonadotropin-releasing hormone (GnRH), growth hormone-releasing hormone (GHRH), dopamine (DA) and somatostatin (growth hormone release inhibiting hormone, GIH) into blood vessels in the hypophyseal portal system. The blood vessels carry the peptides to the anterior pituitary gland, where they regulate the secretion of hormones into the systemic circulation. The parvocellular neurosecretory cells include those that make:
As well as neuroendocrine neurons, the PVN containsinterneurons and populations of neurons that project centrally (i.e., to other brain regions). The centrally-projecting neurons include
The PVN receives afferent inputs from many brain regions and different parts of the body, by hormonal control.[4]
Among these, inputs from neurons in structures adjacent to the anterior wall of the third ventricle (the "AV3V region") carry information about the electrolyte composition of the blood, and about circulating concentrations of such hormones asangiotensin andrelaxin, to regulate the magnocellular neurons.[9]
Inputs from the brainstem (thenucleus of the solitary tract) and the ventrolateral medulla carry information from the heart andstomach. Inputs from thehippocampus to the CRH neurones are important regulators of stress responses.
Inputs fromneuropeptide Y-containing neurons in thearcuate nucleus coordinate metabolic regulation (via TRH secretion) with regulation of energy intake.[10][11][12] Specifically, the projections from the arcuate nucleus seem to exert their effect on appetite viaMC4R-expressing oxytocinergic cells of the PVN.[13]
Inputs fromsuprachiasmatic nucleus about levels of lighting (circadian rhythms).
Inputs from glucose sensors within the brain stimulate release ofvasopressin andcorticotropin-releasing hormone fromparvocellular neurosecretory cells.
