What is the effect of alpha-1 receptor stimulation?

What is the effect of alpha-1 receptor stimulation?

• A. Stimulates contraction of smooth muscles and increases BP via vasoconstriction
• B. Bronchodilation
• C. Vasodilation in skeletal muscle
• D. Decreases heart rate

Answer: (A)

Alpha-1 receptor stimulation causes contraction of smooth muscle, especially in vascular walls, leading to vasoconstriction and a rise in blood pressure due to increased systemic vascular resistance. This works through a Gq pathway that increases IP3 and intracellular calcium, driving smooth muscle contraction. This explains why alpha-1 activation raises blood pressure. By contrast, bronchodilation is a beta-2 effect, skeletal muscle vasodilation is mainly mediated by beta-2 and local factors, and heart rate changes are driven largely by beta-adrenergic receptors, not alpha-1.

Alpha-1 receptor stimulation causes contraction of smooth muscle, especially in vascular walls, leading to vasoconstriction and a rise in blood pressure due to increased systemic vascular resistance. This works through a Gq pathway that increases IP3 and intracellular calcium, driving smooth muscle contraction. This explains why alpha-1 activation raises blood pressure. By contrast, bronchodilation is a beta-2 effect, skeletal muscle vasodilation is mainly mediated by beta-2 and local factors, and heart rate changes are driven largely by beta-adrenergic receptors, not alpha-1.