California scientists working with mice have identified a new compound which could put a halt to migraines. The findings are important since current treatments seldom prevent the recurrence of future headaches in those who suffer from them. The new compound could combat migraines by blocking light sensors found in human eyes. A migraine is a severe type of headache that can be debilitating to many sufferers. Reports say that it affects 29.5 million Americans and is the most-common type of disabling headache for which patients visit physicians.
According to the National Institute of Neurological Disorders and Stroke (NINDS), migraines are three times more common in women than in men. Many sufferers report a family history of these headaches, which can last as long as 72 hours. Common symptoms include nausea and vomiting, pounding in the head and sensitivity to light and sounds. Medical experts haven't found a cure since they don't completely understand migraine pathophysiology. However, despite medications to treat and prevent attacks and patients' lifestyle changes, NINDS says sufferers experience increased sensitivity after each successive episode.
The California researchers identified a series of compounds called opsinamides as blockers of a light sensor in the eye known as melanopsin. They already knew that melanopsin can sense light independently of the normal visual process. It also maintains sleep cycles and causes the pupil of the eye to contract when an individual encounters bright light. This triggers the light sensitivity linked to migraines. Convinced that they could prevent or at least treat migraines if they could block melanopsin, the Salk researchers faced a major obstacle. They needed to find a way to avoid blocking two other types of receptors, rhodopsin and cone opsins, that send information related to vision to the brain.
The scientists tested hundreds of substances. After exposing mice to light, they measured calcium levels, since these levels rise in melanopsin with light exposure. They found that opsinamides blocked any increase in calcium, signifying that they had blocked melanopsin. There was no evidence that the opsinamides interacted with rhodopsin or cone opsins. In addition, the mouse pupils didn't shrink in size, indicating that the chemicals successfully blocked the melanopsin receptor.
The team verified this finding by testing the compounds on mice without melanopsin and found that the substances had no effect. When they used them on newborn mice, which pull away from bright light even before opening their eyes, the mice didn't avoid the light. Once the scientific community fully investigates and develops these compounds, the resulting new drug could prove a way to ward off migraines and also to help those with disrupted sleep patterns.