Which molecule contributes to vasodilation during cerebral autoregulation?

• A. Endothelin-1 causes vasodilation
• B. Angiotensin II
• C. NO contributes to vasodilation during cerebral autoregulation
• D. Vasopressin

Answer: (C)

During cerebral autoregulation, vessels adjust their diameter to keep blood flow to the brain stable despite changes in blood pressure. Nitric oxide is a key mediator of dilation in this process. It is produced by endothelial cells in response to shear stress and metabolic cues, then diffuses into smooth muscle and activates guanylate cyclase to raise cGMP, causing relaxation and widening of the cerebral arterioles. ThisNO-driven dilation helps maintain adequate perfusion when metabolic demand rises or pressure fluctuates. Endothelin-1, angiotensin II, and vasopressin are primarily vasoconstrictors and do not account for the dilation seen in cerebral autoregulation, making NO the best fit.