Beta-2 receptor stimulation results in which effects?

Beta-2 receptor stimulation results in which effects?

• A. Vasodilation and bronchodilation
• B. Vasoconstriction
• C. Increased heart rate
• D. Decreased NE release

Answer: (A)

Beta-2 receptor stimulation mainly causes relaxation of smooth muscle in the airways and in many blood vessels. This happens because beta-2 is a Gs-coupled receptor: activating it raises intracellular cAMP, which activates protein kinase A and reduces calcium-mediated contraction, leading to smooth muscle relaxation. In the lungs, that means bronchodilation; in peripheral vessels, especially in skeletal muscle beds, it means vasodilation. Those two effects—bronchodilation and vasodilation—are the hallmark responses to beta-2 stimulation. Heart rate is more strongly influenced by beta-1 receptors, so increased heart rate isn’t the primary feature of beta-2 activation. There can be some modulatory effects on norepinephrine release via presynaptic beta-2 receptors, but the canonical and most recognizable outcomes are bronchodilation and vasodilation.

Beta-2 receptor stimulation mainly causes relaxation of smooth muscle in the airways and in many blood vessels. This happens because beta-2 is a Gs-coupled receptor: activating it raises intracellular cAMP, which activates protein kinase A and reduces calcium-mediated contraction, leading to smooth muscle relaxation. In the lungs, that means bronchodilation; in peripheral vessels, especially in skeletal muscle beds, it means vasodilation. Those two effects—bronchodilation and vasodilation—are the hallmark responses to beta-2 stimulation.

Heart rate is more strongly influenced by beta-1 receptors, so increased heart rate isn’t the primary feature of beta-2 activation. There can be some modulatory effects on norepinephrine release via presynaptic beta-2 receptors, but the canonical and most recognizable outcomes are bronchodilation and vasodilation.