 It is a neurohypophysial hormone that is transported in vesicles with oxytocin, the other cleavage product, along axons, from magnocellular neurons of the hypothalamus to the posterior lobe of the pituitary.Although it is stored in neurosecretory granules with oxytocin and released with oxytocin, its biological action is unclear.Neurophysin I is carrier protein for oxytocin.