Your humble correspondent has suffered from migraines all his life. He specifically remembers a time in 2nd grade when he complained to his teacher that he had a headache; she sympathetically responded, "So do I." Soon after, he went outside and vomited.
But what causes migraine headaches? For your correspondent, three successive nights with less than 7 hours of sleep is sufficient to trigger a migraine, but so can overly rigorous exercise. Sometimes, they happen for no apparent reason. Unfortunately, your correspondent is afflicted with 2-3 migraines per week, and so far, science hasn't come up with a lot of answers (although it does offer some very effective medications). The underlying reason for the awful, knife-in-your-eyeball sort of pain that accompanies migraines is largely unknown.
What is known is that hyperactive neurons which are then quieted -- a phenomenon known as cortical spreading depression (CSD) -- are responsible for the aura (blurred vision and/or lights) that migraine sufferers typically experience. (See image.) It is also already known that activating the large trigeminal nerve, which is located in the brain and face, causes the pain associated with migraines.
Now, Turkish researchers propose in the journal Science a molecular mechanism that links these two processes.
By poking around in the brains of anesthetized mice, the scientists were able to induce CSD. This caused a neuronal membrane protein channel called Panx1 to open, triggering an inflammatory cascade. Eventually, this inflammation led to activation of the trigeminal nerve, causing mice to experience severe pain. (Scientists can measure pain in mice by examining their facial expressions -- no joke.) When the researchers injected the mice with carbenoxolone, a Panx1 channel blocker, inflammation was reduced, and the mice were rescued from their induced migraine headaches.
Thus, the authors demonstrated that inflammation is the link between CSD and migraine-associated pain. They believe that the inflammatory molecules cause a prolonged stimulation of the trigeminal nerve, which results in unrelenting pain.
If correct, their research opens up a lot of interesting avenues for further research. Perhaps most obviously, determining the effectiveness of different Panx1 channel blockers in reducing and preventing migraines could lead to meaningful discoveries for migraine sufferers.
Your correspondent would urge the authors to pursue this lead rather quickly, as he is feeling yet another migraine coming on.
Source: Hulya Karatas, Sefik Evren Erdener, Yasemin Gursoy-Ozdemir, Sevda Lule, Emine Eren-Koçak, Zümrüt Duygu Sen, and Turgay Dalkara. "Spreading Depression Triggers Headache by Activating Neuronal Panx1 Channels." Science. 1 March 2013: Vol. 339 (6123), pp. 1092-1095. DOI: 10.1126/science.1231897
(Image: Aura via Greensburger/Wikimedia Commons)