<prompt> A patient goes to his family doctor complaining of persistent and severe headaches. His physician diagnoses migraine headaches and prescribes sumatriptan. What is the mechanism of action of this drug?Dopamine 1 agonistGABAB antagonistSerotonin 1D agonistNon-selective beta antagonist  <response>: Sumatriptan is a serotonin 1D agonist that is used to abo migraine headaches. It is also effective in the treatment of cluster headaches. Currently, no dopamine D1 agonists, GABA antagonists, or muscarinic M3 antagonists are used clinically. Propranolol is an example of a non-selective beta antagonist. 