Which intracellular signaling pathway mediates the vascular smooth muscle contraction produced by alpha-1 adrenoceptor activation?

• A Activation of adenylate cyclase with increased cAMP
• B Inhibition of adenylate cyclase with decreased cAMP
• C Gq-mediated phospholipase C activation producing IP3 and DAG ✓
• D Direct opening of potassium channels with membrane hyperpolarization

Explanation

Alpha-1 receptors couple to Gq, activating phospholipase C, which cleaves PIP2 into IP3 and DAG. IP3 releases calcium from the endoplasmic reticulum, causing smooth muscle contraction. Increased cAMP occurs with beta-1 and beta-2 stimulation (Gs), decreased cAMP with alpha-2 (Gi), and potassium channel opening describes some vasodilators like diazoxide, not alpha-1 signalling.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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