Previous studies have shown that increased vasopressin (AVP) concentration to 15 pg/ml in the presence of decreased Na<sup>+</sup> concentration to 121 mM, which mimics AVP-associated hyponatremia in vivo leads to dysfunction, i.e., constriction and impaired endothelial regulation of small intracerebral blood vessels-parenchymal arterioles (PA). Here, AVP is linked to Hyponatremia.