Arginine vasopressin is a human hormone that is released when the body is low on water; it causes the kidneys to conserve water, but not salt, by concentrating the urine and reducing urine volume. It also raises blood pressure by inducing moderate vasoconstriction. Vasopressin is a peptide hormone. It is derived from a preprohormone precursor that is synthesized in the hypothalamus, from which it is liberated during transport to the posterior pituitary. Most of it is stored in the posterior part of the pituitary gland to be released into the blood stream; some of it is also released directly into the brain.

The vasopressins are peptides consisting of nine amino acids (nonapeptides). The amino acid sequence of arginine vasopressin is Cys-Tyr-Phe-Gln-Asn-Cys-Pro-Arg-Gly, with the cysteine residues forming a sulfur bridge. The structure of oxytocin is very similar to that of the vasopressins: it is also a nonapeptide with a sulfur bridge and its amino acid sequence differs at only two positions.

Vasopressin has been implicated in memory formation, including delayed reflexes, image, short- and long-term memory, though the mechanism remains unknown, and these findings are controversial. In recent years there has been particular interest in the role of vasopressin in social behavior. It is thought that vasopressin, released into the brain during sexual activity, initiates and sustains patterns of activity that support the pair-bond between the sexual partners; in particular, vasopressin seems to induce the male to become aggressive towards other males.

Formal Chemical Name (IUPAC)
(S)-N-((R)-1-(2-amino-2-oxoethylamino)-5-(diaminomethyleneamino)-1-oxopentan-2-yl)-1-((4S,7R,10R,13S,16R,19R)-19-amino-7-(2-amino-2-oxoethyl)-10-(3-amino-3-oxopropyl)-13-sec-butyl-16-(4-hydroxybenzyl)-6,9,12,15,18-pentaoxo-1,2-dithia-5,8,11,14,17-pentaaza

References

http://en.wikipedia.org/wiki/Vasopressin