Clonidine reduces sympathetic activity by activating which receptor?

Clonidine reduces sympathetic activity by activating which receptor?

• A. Alpha 1 receptor
• B. Alpha-2 adrenergic receptor
• C. Beta receptor
• D. Dopaminergic receptor

Answer: (B)

Clonidine lowers sympathetic activity by activating alpha-2 adrenergic receptors in the brainstem. These receptors act as inhibitory autoreceptors, and when stimulated they reduce the release of norepinephrine and dampen sympathetic outflow from the CNS. This leads to decreased peripheral vascular resistance and a slower heart rate and blood pressure. The other receptor types don’t fit the action: activating alpha-1 would tend to raise blood pressure via vasoconstriction; beta receptors modulate heart rate and contractility but don’t produce the central dampening effect clonidine uses; dopaminergic receptors aren’t the primary target for this drug.

Clonidine lowers sympathetic activity by activating alpha-2 adrenergic receptors in the brainstem. These receptors act as inhibitory autoreceptors, and when stimulated they reduce the release of norepinephrine and dampen sympathetic outflow from the CNS. This leads to decreased peripheral vascular resistance and a slower heart rate and blood pressure.

The other receptor types don’t fit the action: activating alpha-1 would tend to raise blood pressure via vasoconstriction; beta receptors modulate heart rate and contractility but don’t produce the central dampening effect clonidine uses; dopaminergic receptors aren’t the primary target for this drug.