A new study by Oulu University found large amounts of a light-sensitive OPN4-protein, melanopsin, in the human brain. The mood-enhancing influence and circadian pacemaking properties of bright light when administered through eyes has been shown in earlier studies to be based on the OPN4-protein. In those studies the protein was found only on the retina. This new discovery now confirms that bright light, when channeled through the ear canal into the brain, can have an influence on brain functions.
The study, done at Oulu University, was presented in March at the European Congress of Psychiatry in Prague. The OPN4-protein was originally discovered in 2000 when it was found on the retina. In the more recent study at Oulu University the same protein was found in all the 17 sites of the human brain that were being studied. The presence of the protein was confirmed using methods of molecular biology.
"The discovery of the research team confirms that some of the brain cells may be photosensitive. OPN4-protein, also known as melanopsin, is present in brain cells that have a central role in modulation of several vital functions, including the circadian rhythm", says Professor Seppo Saarela of the Oulu University biology department, who led the study. "Often findings of even classical status are worth re-confirming with additional measurements by several research groups, utilizing improved methods. The present study succeeded in locating melanopsin despite the negative results by the earlier studies. Never before have these measurements been completed on as much human samples as was used in the study now reported", emphasizes Saarela.
The new research findings are supportive of effects of bright light therapy administered directly into the brain through the ear canal.
"Discovery of the photosensitive OPN4-protein in several parts of the human brain adds to the body of evidence that bright light channeled to the brain directly - not just through the eyes - can modulate brain functions", says Chief Science Officer Juuso Nissilä from Finnish company Valkee Oy. The molecules of the opsin family are extremely sensitive to quantities of light that have been already shown in studies decades ago to penetrate all the way into central parts of the brain", he emphasizes.