Which receptor mediates the vasoconstrictive effect of vasopressin on vascular smooth muscle?

Which receptor mediates the vasoconstrictive effect of vasopressin on vascular smooth muscle?

• A. V2 receptors
• B. Beta-adrenergic receptors
• C. Alpha-1 adrenergic receptors
• D. V1 receptors

Answer: (D)

The vasoconstrictive effect of vasopressin on vascular smooth muscle is mediated by V1 receptors. When vasopressin binds to V1 receptors on smooth muscle, these receptors—coupled to the Gq protein—activate phospholipase C, leading to generation of IP3 and DAG. IP3 increases intracellular calcium, triggering smooth muscle contraction and vessel constriction. This V1 pathway is specific to vascular smooth muscle; in contrast, V2 receptors, located mainly in the renal collecting ducts, couple to Gs and promote water reabsorption via increased cAMP and insertion of aquaporin-2. Beta-adrenergic receptors tend to influence heart rate and can cause vasodilation in some beds, while alpha-1 adrenergic receptors mediate norepinephrine-induced vasoconstriction but are not the receptors through which vasopressin exerts its vasoconstrictive effect.

The vasoconstrictive effect of vasopressin on vascular smooth muscle is mediated by V1 receptors. When vasopressin binds to V1 receptors on smooth muscle, these receptors—coupled to the Gq protein—activate phospholipase C, leading to generation of IP3 and DAG. IP3 increases intracellular calcium, triggering smooth muscle contraction and vessel constriction. This V1 pathway is specific to vascular smooth muscle; in contrast, V2 receptors, located mainly in the renal collecting ducts, couple to Gs and promote water reabsorption via increased cAMP and insertion of aquaporin-2. Beta-adrenergic receptors tend to influence heart rate and can cause vasodilation in some beds, while alpha-1 adrenergic receptors mediate norepinephrine-induced vasoconstriction but are not the receptors through which vasopressin exerts its vasoconstrictive effect.