Misoprostol is used for cervical ripening and labour induction. It acts at which prostaglandin receptor subtype predominantly responsible for its uterotonic effects?

• A EP2 and EP4 receptors, which are Gs coupled and mediate smooth muscle relaxation
• B FP receptors on uterine smooth muscle mediating PGF2α-like contraction
• C EP1 and EP3 receptors, which are Gq/Gi coupled and mediate smooth muscle contraction ✓
• D IP receptors on decidual cells mediating prostacyclin-induced cervical softening

Explanation

Misoprostol is a synthetic PGE1 analogue. PGE1 and misoprostol exert their uterotonic effects primarily through EP1 and EP3 receptors, which couple via Gq (EP1, activating IP3/DAG/calcium) and Gi (EP3, reducing cAMP) pathways to promote smooth muscle contraction and enhance myometrial tone. EP2 and EP4 are Gs-coupled, relaxing smooth muscle, while FP receptors mediate the uterotonic action of natural PGF2α (dinoprost). Misoprostol also causes cervical ripening through softening of cervical collagen, partially involving EP2/EP4 pathways locally.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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