(Arg8) Vasotocin (AVT) is a member of the neurohypophyseal hormone family which contains 9 amino acids with the cysteines at positions 1 and 6 linked through a disulphide bridge. Within the central nervous system of lower vertebrates, AVT has been shown to play a role as a neuromodulator and controls reproductive behaviour. Furthermore it regulates osmotic and electrolyte balance and blood pressure within the periphery. In the mammalian brain AVT functions through arginine vasopressin (AVP) or oxytocin receptor cross-reactions. Mice have an AVT reactive receptor specific to AVT and neuropeptide S. This AVT which functions to regulate processes such as sleep and reproduction.