Neuronal Circuits and Neuroendocrine Responses Involved in Dehydration Induced by Water Restriction/Deprivation
A variety of brain regions are involved in sensing alterations of body fluid volume and osmolarity. Circumventricular organs (CVOs) including the subfornical organ (SFO), the organum vasculosum laminae terminalis (OVLT), the median preoptic nucleus (MnPO), and the area postrema (AP) contain copious osmoreceptors and are known as the “sensory complex.” In addition, neurons in the nucleus tractus solitarius (NTS) relay peripheral signals to other areas of the brain, and neurons in the lateral parabrachial nucleus (LPB) integrate information from the hypothalamo-neurohypophyseal system (HNS) or the AP/NTS and act to modulate motor behavior.
Neurons in the supraoptic nucleus (SON) and hypothalamic paraventricular nucleus (PVN), which receive signals from the intrinsic osmoreceptors and the CVOs as well as NTS, release oxytocin (OT) and arginine vasopressin (AVP) into the general circulation to modulate water retention and natriuresis. These processes are also modulated by classic neurotransmitters such as norepinephrine (NE), glutamate, γ-aminobutyric acid (GABA), nitric oxide (NO), and many other neuropeptide transmitters such as angiotensin II (AngII), corticotrophin-releasing hormone (CRH), apelin, galanin, estrogens (Es), obestatin, orexin, and neuropeptide Y (NPY).
In addition to OT, AVP and some other known genes being up- or downregulated, several novel genes are thought to be involved in neuronal responses to dehydration.
Glia may also influence water and salt balance via modulation of sodium-level-sensitive sodium channels (Nax), aquaporin-4 water channels (AQP4), and secretion of taurine in CVOs and the HNS.
KeywordsAtrial Natriuretic Peptide Water Deprivation Nucleus Tractus Solitarius Area Postrema Orexin Neuron
Anteroventral third ventricle area
Anteroventral part of PVN
Bed nuclei of the stria terminalis
Central amygdaloid nucleus
Central nervous system
Corticotropin releasing hormone
Glial fibrillary acidic protein
Lateral parabrachial nucleus
Magnocellular neurosecretory cells
Medial amygdaloid nucleus
Median preoptic nucleus
Nucleus tractus solitarius
Organum vasculosum of the lamina terminalis
Hypothalamic paraventricular nucleus
- Samson WK, White MM, Price CP, Ferguson AV. Am J Physiol. 2007;292:R637–43.Google Scholar