Posterior Pituitary Agents

The neurohypophysis releases oxytocin and vasopressin which are synthesized in the hypothalamus. In addition to its classical effects on renal water reabsorption and the contraction of vascular smooth muscle cells, it regulates corticotrophin secretion and has numerous non-endocrine effects, including acting as a central neurotransmitter. It acts through three receptors V 1a , V 1b , and V 2 , with the renal receptor being V 2 . V 2 receptor antagonists are used to treat hyponatremia due to inappropriate vasopressin secretion and are being investigated for heart failure. Oxytocin stimulates uterine contractility and milk ejection but has numerous other effects, because the oxytocin receptor is widely distributed.