Evolution of the arginine-vasopressin system: from chordates to primates

The neurohypophysal system is one of the most ancient and important system controlling and maintaining the intra- and extravascular volume and osmotic homeostasis in vertebrates. It works via the kidney control of water reabsorption, via the central thirst control and finally via the regulation of arterial vasoconstriction and consequently of blood pressure. The phylogenetic analysis of neurohypophysal system development shows that some of its components were already present in several marine invertebrates, in Branchiostoma floridae and in the cyclostomate Lampetra fluvialis, but their functions are not yet completely clarified. It is with the first vertebrate gnathostomes that a structural system appeared with two hormones (vasopressin and oxytocin analogues), but only with the amphibians the system is completely functioning to maintain the internal environment stability independently from the external one. This article provides information about the phylogenenic appearance and the main structural and functional modifications of the neurohypophysal system, and in particular of the arginine vasopressin, from the first vertebrates until amphibians, mammalians and primates.