Clonidine produces sedation and reduces blood pressure primarily by acting on which receptor subtype and through which second messenger pathway?

• A α1-adrenoceptors; activation of phospholipase C increasing IP3
• B Imidazoline I1 receptors; activation of adenylyl cyclase increasing cAMP
• C α2-adrenoceptors; inhibition of adenylyl cyclase reducing cAMP ✓
• D β2-adrenoceptors; activation of adenylyl cyclase increasing cAMP

Explanation

Clonidine acts as a full agonist at presynaptic and postsynaptic α2-adrenoceptors, which are Gi-coupled; activation inhibits adenylyl cyclase, reducing intracellular cAMP. Its central antihypertensive effect results from reduced sympathetic outflow from the brainstem, while its sedative effect is mediated by α2A receptors in the locus coeruleus. Imidazoline I1 receptors contribute secondarily in the rostral ventrolateral medulla but are not the primary mechanism for either action.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.