When the sun’s ultraviolet light hits the skin, the gene activity increases in the skin cells. POMC… It encodes a protein that, after synthesis, is cut into peptides that have their own functions. In particular, some of the peptides from the POMC protein stimulate the synthesis of the pigment melanin, which is supposed to protect us from UV radiation. And there are other POMC peptides that stimulate endorphin synthesis. We know that endorphins are endogenous opioids – these are special molecules that act on opioid receptors on the neurons of the brain, due to which they soften pain, and also give a feeling of happiness, euphoria, etc. (however, the functions of endorphins are not limited to these).
In a similar way, opiate drugs like heroin or morphine act on the brain, which cause permanent addiction. The suspicion arises that endorphins can also cause addiction, and then the individual will constantly do what causes the release of endorphins. Indeed, in experiments, mice managed to induce an addiction to ultraviolet light: they were constantly looking for where to be irradiated, and their behavior was similar to how if they were morphine addicted and they would constantly run to the source of morphine. Actually, that there are mice – there are studies about people who constantly sunbathe, and about whom we can say that they have become addicted to ultraviolet radiation.
But ultraviolet light also triggers the synthesis of vitamin D. It occurred to staff at Harvard University and Massachusetts Central Hospital that ultraviolet light, vitamin D and opioid addiction might somehow be related. An analysis of medical statistics showed that people with a lack of vitamin D are 50% more likely to take opioid pain relievers; if there is very little vitamin D in the body, then the addiction to opioids increases by 90%. (When analyzing statistics covering about 20 thousand patients, we took into account age, gender, chronic pain, if any, and many other factors.)
After that, they moved on to experiments on mice, in which the level of vitamin D was lowered or simply by genetic engineering they turned off the receptors for it so that the cells could not feel it. The mice were then placed in a chamber with several rooms in which different portions of morphine could be found, and observed where the animals would stay the longest.
Mice that were doing well with vitamin D preferred rooms with the highest dose of morphine. But mice that had problems with vitamin D (either they did not have it at all, or they were immune to it) seemed to agree to a lower dose of the opiate. Their sensitivity to morphine increased fourfold, that is, a fourfold smaller dose was enough for the mouse to remain in the morphine room for a long time, waiting for a new portion. The experiments were repeated in different modifications, but the result remained the same: the lack of vitamin D made the mice more sensitive to morphine.
On the other hand, as stated in the article in Science Advances, morphine as a pain reliever in “vitamin-free” mice acted with greater efficiency. Vitamin D deficient mice suffered longer pain after receiving a dose of the opiate. The sensitivity to pain increased if the animals had increased levels of vitamin D, and similarly it increased if their opioid receptors were turned off, which proved the link between vitamin D and the opioid system.
In other experiments, mice lacking vitamin D receptors were irradiated with ultraviolet light – and their sensitivity to pain decreased, unlike normal mice, in which cells were sensitive to the vitamin. In addition, mice that are immune to the vitamin tended to sit longer in ultraviolet rooms, as if there were morphine rather than ultraviolet light.
Obviously, vitamin D somehow suppresses the work of the opioid system: because of it, the brain’s sensitivity to endorphins and other substances that act on opioid receptors decreases (perhaps the number of receptors decreases, perhaps some other mechanism is triggered). And if the animal does not have enough vitamin D, it will tend to get out in the sun – because it will be especially pleasant for it, because there is too little vitamin D, and there will be more pleasure from endorphins. Well, when the level of the vitamin rises, the craving for the sun will diminish by itself.
But if we talk about drugs, then a person is more likely to increase the dose than refuse to take them. And it is unlikely that vitamin D can somehow be used to treat addictions. Nevertheless, it is possible that the level of vitamin D can really assess a person’s susceptibility, for example, to painkillers, and assess the likelihood of dependence on such drugs.
Based on materials The Scientist.
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