Which statement is true about Clonidine's mechanism?

Which statement is true about Clonidine's mechanism?

• A. It increases sympathetic activity
• B. It decreases sympathetic activity
• C. It has no effect on sympathetic activity
• D. It increases parasympathetic activity

Answer: (B)

Clonidine reduces sympathetic outflow from the central nervous system by activating central alpha-2 adrenergic receptors (and related imidazoline receptors). This inhibits norepinephrine release from presynaptic neurons, especially in the brainstem, leading to decreased sympathetic tone. The result is lower peripheral vascular resistance and heart rate, manifesting as reduced blood pressure. Therefore, the key point is that clonidine decreases sympathetic activity. It does not increase sympathetic activity, nor does it act by increasing parasympathetic activity directly.

Clonidine reduces sympathetic outflow from the central nervous system by activating central alpha-2 adrenergic receptors (and related imidazoline receptors). This inhibits norepinephrine release from presynaptic neurons, especially in the brainstem, leading to decreased sympathetic tone. The result is lower peripheral vascular resistance and heart rate, manifesting as reduced blood pressure. Therefore, the key point is that clonidine decreases sympathetic activity. It does not increase sympathetic activity, nor does it act by increasing parasympathetic activity directly.