TRPV1, Migraine, and Sumatriptan
What on earth is TRPV1? TRPV1 is an ion channel brain receptor - the long name is transient receptor potential vanilloid 1 (for you biology geeks). It is also known as the capsaicin receptor.
TRPV1 is activated by chemical irritants, inflammatory mediators, and physical mediators of tissue damage, like high temperatures and acid pH. The TRPV1 receptors are located in skin, tissues of the airways, gastrointestinal linings, and the outer coverings of the eye (cornea and conjunctiva). It has also been identified in various areas of the brain. It is thought to have a central role in neurogenic inflammation.
Although the fucntions of TRPV1 are still being identified, its role in central nervous system inflammation has made it a target for migraine research, as it may possibly play a role in causing hyperalgesia and allodynia. TRPV1 is thought to affect cranifacial pain via the trigeminal nerve system, in addition to other painful conditions. Various new drugs that are TRPV1 antagonists are in development for various painful conditions, including migraine.
However, we already have an existing drug for migraine that has TRPV1 activity. Sumatriptan (Imitrex®, Imigran®, Sumavel®, Alsuma®) has been found to block the effects of capsaicin (the substance that makes chili peppers hot) on the trigeminal neurons in the brainstem. This confirms the role of TRPV1 receptors in the migraine process, and helps our understanding of migraine pathways. It may lead us to new therapies.