Diuresis used to increase urine output and decrease extracellular fluid volume. Substances in the circulation can also increase the amount of circulating fluid by increasing the osmolarity of the blood. This has the effect of pulling water from the interstitial space, making more water available in the blood and causing the kidney to compensate by removing it as urine. In hypotension, often colloids are used intravenously to increase circulating volume in themselves, but as they exert a certain amount of osmotic pressure, water is therefore also moved, further increasing circulating volume. As blood pressure increases, the kidney removes the excess fluid
Subfornical organ columns and body of the fornix. Afferent fibers from the body and columns of the fornix polysynaptically excite both superficial and deep neurons. A recurrent inhibitory circuit is suggested on the output path. The expression of various genes in the subfornical organ have been studied. For example, it was seen that water deprivation in rats led to an upregulation of the mRNA that codes for angiotensin II receptors, allowing for a lower angiotensin concentration in the blood that produce the "thirst" response. It also has been observed to be a site of thyroid transcription factor 1 (TTF1) production, a protein