Central regulation of body-fluid homeostasis.

Body-fluid homeostasis is essential to life, and the concentration of Na(+) ([Na(+)]) and osmolality in plasma and the cerebrospinal fluid (CSF) are continuously monitored in the brain. To maintain a physiological level of Na/osmolality in body fluids, the control of Na and water intake and excretion are of prime importance. Two independent sensing systems for [Na(+)] and osmolality in circumventricular organs (CVOs) have long been postulated to be involved in the monitoring of body-fluid conditions. In the past decade, several molecules were reported as promising candidates for these sensors - Nax for the [Na(+)] sensor and transient receptor potential (TRP) channels for the osmosensor. This review presents a summary of developments in these areas over recent years.