The maintenance of plasma sodium concentration withina narrow limit is crucial to life. When it differs from normalphysiological patterns, several mechanisms are activated in orderto restore body fluid homeostasis. Such mechanisms may bevegetative and/or behavioral, and several regions of the centralnervous system (CNS) are involved in their triggering. Some ofthese are responsible for sensory pathways that perceivea disturbance of the body fluid homeostasis and transmitinformation to other regions. These regions, in turn, initiateadequate adjustments in order to restore homeostasis. The maincardiovascular and autonomic responses to a change in plasmasodium concentration are: i) changes in arterial blood pressureand heart rate; ii) changes in sympathetic activity to the renalsystem in order to ensure adequate renal sodiumexcretion/absorption, and iii) the secretion of compoundsinvolved in sodium ion homeostasis (ANP, Ang-II, and ADH, forexample). Due to their cardiovascular effects, hypertonic salinesolutions have been used to promote resuscitation inhemorrhagic patients, thereby increasing survival rates followingtrauma. In the present review, we expose and discuss the role ofseveral CNS regions involved in body fluid homeostasis and theeffects of acute and chronic hyperosmotic challenges.
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