Vasopressin (ADH, AVP) is the hormone which controls the production of urine in the bladder. It is secreted by the pituitary gland based on the salt concentration of the blood. It is negative feedback: the more concentrated the salt in the blood is, the more vasopressin is secreted, which in turn makes the kidney tubules more permeable, allowing more water to be reabsorbed into the blood and creating less, but more concentrated, urine. It also triggers feelings of thirst.
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Avp is expressed in the periventricular region of the hypothalamus in the adult mouse. Allen Brain Atlases
Chemical structure of the arginine vasopressin (argipressin) with an arginine at the 8th amino acid position. Lysine vasopressin differs only in having a lysine in this position.
Chemical structure of oxytocin
Vasopressin Facts for Kids. Kiddle Encyclopedia.