US, WASHINGTON (ORDO NEWS) — Probably, every sweet tooth noticed that the cake from the fridge does not seem so sweet as fresh and still warm – terribly attractive, despite all the harm . This effect was noticed a long time ago, but now the team at the University of California at Santa Barbara, Craig Montell, managed to demonstrate it on flies, and at the same time to understand the molecular mechanisms of weakening the sweet taste. As it turned out, the taste buds of sweets themselves have nothing to do with it.
In an article published in the journal Current Biology , scientists note that laboratory Drosophila show a marked decrease in cravings for sweets at a temperature of 19 ° C, compared with the same dish at a temperature of 23 ° C. At the same time, the receptors perceiving a sweet taste in the flies worked the same way in both cases. “And since the temperature does not directly affect“ sweet ”neurons, it should affect some other cells, indirectly changing the craving for sweets,” says Professor Montel.
It is worth saying that in Drosophila, sweet perceives one particular type of receptor cell, bitter perceives another, and the third type of cell plays the role of mechanoreceptors, perceiving the texture of food. With temperature, everything is somewhat more complicated: both bitter receptors and mechanoreceptors react to it, and only if both types of neurons “work”, this signal will be interpreted as “cold”.
Thus, the activation of Drosophila for food is reduced by the activation of bitter taste receptors, mechanoreceptors (signaling hardness), as well as those and others (reaction to low temperature). The sweet receptors themselves do not respond to cold, but the mechanoreceptors and bitter receptors activated by them block the signal that “sweet” neurons transmit to the brain and reduce cravings for insufficiently warm food.
To the great surprise of scientists, it turned out that the basis of this mechanism is the protein rhodopsin 6 (Rh6), a close relative of the pigment that receives light in our eyes. Thus, suppression of Rh6 expression in bitter receptor cells blocked their response to sensation of cold. As a result, the flies attacked with equal pleasure both warm and cold – if only sweet – food.
According to biologists, this may be due to the peculiarities of insect metabolism, which is highly dependent on external temperature. In the cold, it slows down significantly: for example, at 25 ° C the development of an egg takes about 10 days, and at 18 ° C it is already twice as long, for 20. “Everything slows down,” Craig Montell adds, “and food consumption decreases. You just don’t need it anymore.”
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