Oxytocin and vasopressin

This chapter argues that oxytocin and vasopressin are both nonapeptides and their sites and manner of production and release. It presents important physiological actions of oxytocin and vasopressin and the factors that promote their release. The chapter describes the factors that control oxytocin and vasopressin release and mechanisms of action. It examines the consequences of failed vasopressin release and the treatment. Oxytocin is packaged in a secretory granule as part of a larger protein called neurophysin I. The granule is transported down the nerve axon through the median eminence of the hypothalamus and terminates at capillaries supplying the posterior pituitary gland; oxytocin is cleaved from neurophysin 1 to release biologically active oxytocin into the circulation. Actions of oxytocin are mediated by a membrane-associated oxytocin receptor, which is a member of the rhodopsin-type. The oxytocin receptor requires Mg²⁺ and cholesterol.