The narrowing of blood vessels—it raises blood pressure and reduces blood flow to tissues.Vasoconstriction is the contraction of vascular smooth muscle, decreasing vessel diameter and increasing peripheral resistance and blood pressure. Endogenous vasoconstrictors include angiotensin II, endothelin-1, norepinephrine, and vasopressin (ADH). Desmopressin (DDAVP) is a vasopressin analog modified to retain V2 receptor (renal) selectivity while minimizing V1a receptor (vascular smooth muscle) vasoconstrictor effects—this selective design is why desmopressin treats diabetes insipidus without causing significant hypertension.