A patient is given sumatriptan for acute migraine. Which receptor subtype does sumatriptan primarily agonize to relieve migraine?

• A 5-HT1B/1D receptors ✓
• B 5-HT2A receptors
• C 5-HT3 receptors
• D 5-HT4 receptors

Explanation

Triptans (sumatriptan, zolmitriptan, rizatriptan) are selective 5-HT1B/1D receptor agonists. Activation of 5-HT1B receptors on the smooth muscle of intracranial extracerebral blood vessels causes selective cranial vasoconstriction, reversing the dilatation associated with migraine. Activation of 5-HT1D receptors on trigeminal nerve terminals inhibits release of vasodilatory neuropeptides (CGRP, substance P). Together these mechanisms terminate the headache. 5-HT2A activation (by ergotamine) also causes cranial vasoconstriction but with less selectivity. 5-HT3 and 5-HT4 receptors are not therapeutic targets in migraine.

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

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