Mechanisms of action of sumatriptan and ergotamine

Sumatriptan:

• highly selective agonist of the D subtype of 5-HT1 - these are located on peripheral trigeminal-nerve terminals that supply pain-sensitive vascular and meningeal structures.
• selective for a subtype of 5-HT1 receptors located on intracranial vessels, where it mediates contraction, particularly of large arteries - the direct vasoconstrictive action of sumatriptan may also alleviate headache.
• calcitonin-gene-related peptide is released into jugular venous blood during a migraine attack - this release is blocked by sumatriptan.
• blocks the neuropeptide-mediated inflammatory response after trigeminal stimulation.

Ergotamine:

• has high affinity but less selectively for 5-HT1 receptors.
• dihydroergotamine is a potent venoconstrictor - also has arterial vasoconstrictor effects, which may alleviate headache.