Neuronal Circuits Involved in Osmotic Challenges

Abstract

The maintenance of plasma sodium concentration within a narrow limit is crucial to life. When it differs from normal physiological patterns, several mechanisms are activated in order to restore body fluid homeostasis. Such mechanisms may be vegetative and/or behavioral, and several regions of the central nervous system (CNS) are involved in their triggering. Some of these are responsible for sensory pathways that perceive a disturbance of the body fluid homeostasis and transmit information to other regions. These regions, in turn, initiate adequate adjustments in order to restore homeostasis. The main cardiovascular and autonomic responses to a change in plasma sodium concentration are: i) changes in arterial blood pressure and heart rate; ii) changes in sympathetic activity to the renal system in order to ensure adequate renal sodium excretion/absorption, and iii) the secretion of compounds involved in sodium ion homeostasis (ANP, Ang-II, and ADH, for example). Due to their cardiovascular effects, hypertonic saline solutions have been used to promote resuscitation in hemorrhagic patients, thereby increasing survival rates following trauma. In the present review, we expose and discuss the role of several CNS regions involved in body fluid homeostasis and the effects of acute and chronic hyperosmotic challenges.

Up‐regulation of hypothalamic arginine vasopressin by peripherally administered furosemide in transgenic rats expressing arginine vasopressin‐enhanced green fluorescent protein

“…Central osmoreceptors are localised in the vascular organ of the lamina terminalis (OVLT) and the subfornical organ (SFO), which are known as the circumventricular organ. The osmosensitive neurones in the OVLT and SFO project their axons to the SON and PVN to regulate the activity of AVP neurones . On the other hand, hypovolaemia is perceived by pressure and volume sensors.…”

“…administration of furosemide. In addition, we counted Fos‐IR cells in the OVLT, median preoptic nucleus (MnPO), SFO, arcuate nucleus (Arc), locus coeruleus (LC), area postrema (AP), NTS and RVLM, which were reported to be involved fluid homeostasis by control of AVP synthesis and/or have an interaction with the hypothalamus . Finally, gene expression of AVP heteronuclear RNA (hnRNA), AVP mRNA ( AVP ) and eGFP mRNA ( eGFP ) in the hypothalamus was evaluated after i.p.…”

Colocalized neurotransmitters in the hindbrain cooperate in adaptation to chronic hypernatremia

“…Several central behavioral, autonomic and hormonal reactions are triggered by the increased plasma sodium level. These include the generation of thirst, reducing sodium appetite, increasing renal sodium excretion and water retention, elevation of blood pressure and parallel activation of renal sympatho-inhibition (Bourque 2008;Dos Santos Moreira et al 2017). Noradrenergic inputs to the SON, PVN and the AV3V from the A1 and A2 cell groups are essential to trigger these reactions (Fernandez-Galaz et al 1994;Pedrino et al 2005Pedrino et al , 2008Pedrino et al , 2012Dos Santos Moreira et al 2017).…”

Oxytocin‐monomeric red fluorescent protein 1 synthesis in the hypothalamus under osmotic challenge and acute hypovolemia in a transgenic rat line

“…Hypothalamic AVP synthesis is known to be upregulated mainly under hyperosmolality and hypovolemia (Arima et al, 1999;Dunn et al, 1973;Kondo et al, 2004). The vascular organ of the lamina terminalis (OVLT) and the subfornical organ (SFO), brain regions known as the circumventricular organs (CVOs), sense the change in plasma osmolality Dos santos moreira et al, 2017). The anatomical feature of lacking a blood-brain barrier enables CVOs to directly sense the change in plasma osmolality.…”