Paraventricular nucleus of hypothalamus
The paraventricular nucleus (PVN, PVA, or PVH) is a nucleus in the hypothalamus. Anatomically, it is adjacent to the third ventricle and many of its neurons project to the posterior pituitary. These projecting neurons secrete oxytocin and a smaller amount of vasopressin, otherwise the nucleus also secretes corticotropin-releasing hormone (CRH) and thyrotropin-releasing hormone (TRH).[1] CRH and TRH are secreted into the hypophyseal portal system and act on different targets neurons in the anterior pituitary. PVN is thought to mediate many diverse functions through these different hormones, including osmoregulation, appetite, and the response of the body to stress.[2]
Not to be confused with Periventricular nucleus.Paraventricular nucleus of hypothalamus
Location[edit]
The paraventricular nucleus lies adjacent to the third ventricle. It lies within the periventricular zone and is not to be confused with the periventricular nucleus, which occupies a more medial position, beneath the third ventricle. The PVN is highly vascularised and is protected by the blood–brain barrier, although its neuroendocrine cells extend to sites (in the median eminence and in the posterior pituitary) beyond the blood–brain barrier.
Afferent inputs[edit]
The PVN receives afferent inputs from many brain regions and different parts of the body, by hormonal control.[2]
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 as angiotensin and relaxin, to regulate the magnocellular neurons.[5]
Inputs from the brainstem (the nucleus of the solitary tract) and the ventrolateral medulla carry information from the heart and stomach. Inputs from the hippocampus to the CRH neurones are important regulators of stress responses.
Inputs from neuropeptide Y-containing neurons in the arcuate nucleus coordinate metabolic regulation (via TRH secretion) with regulation of energy intake.[6][7][8] Specifically, the projections from the arcuate nucleus seem to exert their effect on appetite via MC4R-expressing oxytocinergic cells of the PVN.[9]
Inputs from suprachiasmatic nucleus about levels of lighting (circadian rhythms).
Inputs from glucose sensors within the brain stimulate release of vasopressin and corticotropin-releasing hormone from parvocellular neurosecretory cells.