OXITOCINA

Oxytocin is a mammalian neurohypophysial hormone that acts primarily as a neuromodulator in the brain

http://en.wikipedia.org/wiki/Oxytocin

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The neurohypophysial hormones form a family of structurally and functionally related peptide hormones. Their main representatives are oxytocin and vasopressin. They are named for being secreted by the neurohypophisis, i.e. the posterior pituitary gland (hypophysis refers to the pituitary gland), itself a neuronal projection from the hypothalamus.

http://en.wikipedia.org/wiki/Neurohypophysial_hormone