AVP and essential hypertension: Increased circulating ADH levels have also been reported in prehypertensive young and hypertensive middle-aged spontaneously hypertensive rats (SHR), the most widely used animal model of human essential hypertension (30), as compared to their normotensive controls Wistar Kyoto (WKY), but not in the SHR-stroke-prone strain, where ADH levels were markedly reduced (31, 32).