Arcuate nucleus
Nucleus arcuatus (infundibularis)
Also known as: infundibular nucleus
A crescent of small neurons around the base of the third ventricle above the median eminence that secretes GHRH, dopamine and (with the preoptic area) GnRH, and integrates leptin, insulin and ghrelin signals to control appetite.
Overview
The arcuate (infundibular) nucleus sits in the tuberal hypothalamus, hugging the floor of the third ventricle where it enters the median eminence. Because the adjacent median eminence lacks a blood–brain barrier, arcuate neurons are directly exposed to circulating hormones.
Neuroendocrine populations include GHRH neurons, tuberoinfundibular dopamine (A12) neurons that tonically inhibit prolactin secretion, and KNDy neurons (kisspeptin, neurokinin B, dynorphin) that generate the pulsatile release of GnRH from GnRH nerve terminals in the median eminence. Two antagonistic appetite populations — anorexigenic POMC/CART neurons and orexigenic NPY/AgRP neurons — respond to leptin, insulin and ghrelin and project to the paraventricular nucleus and lateral hypothalamus.
- Location
Tuberal hypothalamus, at the base of the third ventricle immediately above the median eminence.
Function
- GHRH secretion (stimulates GH).
- Dopamine secretion (prolactin-inhibiting hormone).
- GnRH pulse generation via KNDy neurons.
- Integration of long-term (leptin, insulin) and short-term (ghrelin) energy signals.
Clinical significance
Antipsychotic-induced hyperprolactinaemia
D2-receptor blockers (risperidone, haloperidol) and metoclopramide block the action of tuberoinfundibular dopamine on lactotrophs → galactorrhoea, amenorrhoea, sexual dysfunction.
Monogenic obesity
Mutations in leptin, the leptin receptor, POMC or MC4R disrupt this circuit and cause early-onset severe obesity with hyperphagia; MC4R defects are the commonest.
Compiled from standard anatomy and physiology references — see the Endocrine System sources. For education only; not medical advice.