Ephedrine raises blood pressure through both direct and indirect mechanisms. The indirect component of its sympathomimetic action involves which mechanism?

• A Inhibition of catechol-O-methyltransferase in the liver
• B Upregulation of beta-adrenoceptor expression on vascular smooth muscle
• C Displacement of norepinephrine from sympathetic nerve terminal vesicles ✓
• D Inhibition of norepinephrine reuptake via the norepinephrine transporter

Explanation

Ephedrine is an indirect-acting sympathomimetic that displaces norepinephrine from storage vesicles in sympathetic nerve terminals, releasing endogenous catecholamine into the synaptic cleft. It also has direct agonist activity at alpha and beta receptors. COMT inhibition, reuptake inhibition (cocaine/TCAs), and receptor upregulation are not the primary indirect mechanisms of ephedrine.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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