Sun is similarly dependent on heroin

Sunbathing can make you dependent

06/20/2014

Although UV rays significantly increase the risk of skin cancer, many people have a great desire for sunbathing. This seemingly instinctive behavior was recently followed by US researchers. According to their study, regular sunbathing is similar to drug use. Mice exposed to UV radiation for several weeks showed typical withdrawal symptoms when they received a drug that blocked the radiation-induced formation of certain substances.

Desire for sunbathing has evolved
UV radiation is considered to be highly carcinogenic to the skin. Nevertheless, many people feel the need to expose themselves to intense solar radiation. A research team led by David Fisher of the Massachusetts General Hospital in Boston wondered why the craving for sunbathing could have evolved in the course of evolution. They suspected that there might be a relationship to the vitamin D level in the blood.

When UV radiation hits the skin, several processes are triggered: The horn-forming cells begin to produce the protein proopiomelanocortin (POMC), which in turn is a precursor to various messengers. Thus, with the help of POMC, a hormone can be formed which produces the skin pigment melanin. The body's painkiller beta-endorphin is also made from POMC. Beta-endorphin is particularly interesting in this context, because it binds similar to heroin and some other drugs or drugs such as morphine to the so-called opioid receptors and thus unfolds its analgesic effect.

In the context of their study, the researchers wanted to find out whether UV radiation, not only in the skin but also in the blood, causes a change in the beta-endorphin level, the effect of which is pain-relieving and at the same time dependent.
Mice showed dependence on UV radiation
For their study, mice who had their backs shaved were exposed to UV radiation regularly over a period of six weeks, five days a week. The dose was chosen so that the animals were browned but not burned. As the researchers report, the radiation intensity was about that of a fair-skinned person exposed to a 20 to 30-minute sunbathing in Florida. After just one week, the researchers detected an increased beta-endorphin level in the blood of the rodents. In addition, they were more resistant to pain. In the next step, a drug was administered to some animals that blocked the action of beta-endorphin on the opioid receptors. The mice treated with the drug reacted with withdrawal symptoms such as tremors and teeth chattering. In addition, they kept away from the place where they received the drug.

As a control, other mice were genetically engineered to produce either none or only their skin cells could not produce beta-endorphin. They showed no response to UV radiation in terms of their sensitivity to pain. The gift of the drug had no effect.

„It is surprising that we are genetically programmed to become dependent on something as dangerous as UV radiation - probably the most prevalent carcinogen in the world, "the news agency quoted „dpa“ Study author Fisher.

Perhaps the urge to sunbathe could be related to vitamin D levels, the researchers suggest, as the formation of vitamin D is stimulated by UV radiation and plays an important role in bone formation.

„Although the initial UV addiction - mediated by the hedonic action of beta-endorphin and the contrasting effects of withdrawal - could theoretically have favored evolutionary vitamin D biosynthesis, it is now contributing to the steady increase in skin cancers in humans“, the researchers write in the journal „Cell“, in which they published their study results. (Ag)