Ural Federal University: Scientists Found an Evolutionary Link in Pain Reactions in Fish and Humans

A group of scientists from universities in Russia and Brazil investigated the effect of gender on the tolerance of pain and fear in laboratory zebrafish. The research contributes to the development of medications that alleviate pain by taking into account the gender of the patient.

So far, the relationship between pain and gender in zebradanio has been poorly studied, although this freshwater fish species has a large, 70% genetic similarity to humans, related physiology, neuroanatomy and neurochemistry. Thus, zebradanios are a good model for studying how the brain responds to pain or fear. The researchers’ paper describing the experiments and their results is published in the journal Neuroscience Letters.

In the work, the “collective” of male and female zebradanios was divided into control and experimental groups. For the first experiment, to determine the body’s response to pain, researchers selected 12 males and females each. They were injected with a solution and run in a test tank. For a few minutes recorded changes in their behavior compared to the control, untreated group of individuals. Both males and females involved in the experiment reacted to pain by climbing up to the upper level of the aquarium less often, more often to the bottom, which was safer for them, slowed down their movement in the water, froze in torpor. At the same time, the behavior of females was more pronounced, and their reactions to stress by pain were more frequent and longer lasting.

In the second experiment, scientists investigated the behavioral responses of zebradanio to a source of fear. For this purpose, nine males and females each were placed for a few minutes in a vessel with a substance pheromone of fear, which causes severe anxiety in fish. In this experiment, behavioral changes in the individuals were equally strong and independent of their gender. As in the first experiment, the fish slowed down, stopped, and froze more frequently than the individuals in the control group, and also swam up to the water surface less frequently.

“It is known, for example, that female rodents are more sensitive to pain than males, and the same can generally be said about female reactions to pain. Therefore, our experiments indicate that gender differences in reactions to pain have persisted in the course of evolution, from fish to mammals. This means that animals such as zebradanio, which are fast breeding, unpretentious, inexpensive to keep and therefore so convenient for biomedical experiments, can be used for search and creation of new drugs capable of reducing pain sensitivity with regard to sex differences”, commented Alan Kaluev, head of research, leading researcher of Ural Federal University, member of European Academy, professor of Saint Petersburg State University and Scientific and Technical University.

The conducted scientific work fully corresponds to the concept of the state Strategy for Scientific and Technological Development of Russia, one of the priorities of which is the promotion of personalized medicine. On the Russian side, the scientists’ research was supported by the Russian Science Foundation, the Russian Academician A.M. Granov Research Center for Radiology and Surgical Technologies, and the Sirius Scientific and Technological University.

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