A type of cell present in the eye that is crucial to promote sleep during the night and in general for the body’s recognition of circadian rhythms was discovered by a group of researchers at the Salk Institute that published a study on Cell Reports.
According to the researchers, these cells are able to detect light and “align” the same circadian rhythm of the brain with ambient light. These are intrinsically photosensitive retinal ganglion cells (ipRGC) and, according to the researchers themselves, can have heavy health implications.
The same circadian rhythm is proving to be increasingly important, with research carried out in recent years: it regulates the day-night rhythm of the body and, if irregular, can trigger various diseases, first of all insomnia, which can then in turn lead to diseases or other more serious diseases. This becomes even more important if we think about this era, a period in which we spend most of our lives inside closed structures where natural light is no longer decisive and artificial light is mostly used at all hours.
If we think that for hundreds of thousands or millions of years human beings, and their ancestors, have essentially lived with daylight and almost complete darkness at night, such an upheaval, which has occurred mostly in the last thousands of years but more intensively in the last 150 years with the use of electricity for lighting, must have had clear consequences on the body and the circadian rhythms themselves.
So understanding how IPRGCs respond to the quantity, duration and sequences of light can be very useful, for example, to design new lighting technologies, especially in those environments where there are more sensitive subjects such as in the neonatal sections of hospitals, care centers, schools or even in other public places such as factories, hospitals, offices, retirement homes, etc., as Satchidananda Panda, the senior author of the study, explains very clearly.
HypRGCs had already been identified previously in the retinas of mice but this is the first time that their presence is also reported in humans. The researchers used a particular method to keep the retinal samples healthy and functional after they had been taken from human bodies after death.
They were able to analyze these samples with special electrodes to understand how they reacted to light by also testing various sequences, various levels of intensity and various colors. Among other things, they confirmed that these cells seem “inherently photosensitive” and in general more sensitive to blue light, the light that is usually used in most of the LEDs we see around and on the screens of our devices, from those for the computer to those of mobile devices or smartphones.