In experiments with zebrafish, scientists have discovered a new hormone — secretoneurin. Individuals of the organism which does not produce secretoneurin due to a mutation, couldn’t spawn, but his artificial injection increased success in reproductive behaviour. As noted by the authors in the journal Proceedings of the National Academy of Sciences, similar hormones likely regulate reproduction and other vertebrates, including humans.
Fish zebrafish (Danio rerio) multiply rapidly, and the activity of their genes are easy to manipulate, so it is one of the popular model organisms for biologists. Working with this form, scientists can understand all the features of vertebrate embryogenesis, aging, and sexual behavior.
Some time ago it turned out that zebrafish, which mutations are not produced sex hormones kisspeptin and leaks on behavior do not differ from normal relatives. Scientists have suggested that the lack of these important compounds kompensiruet at the expense of another hormone, which is yet unknown to science.
One of the candidates for the role of this hormone — protein secretogranin-2, which is mainly found in neurons and cells of the endocrine system. The researchers, led by Vance Trudeau (Trudeau Vance L.) from the University of Ottawa analyzed the function of this compound. For this they brought out a line of zebrafish, an organism which does not produce secretogranin-2 due to mutations in the genes scg2a or scg2b.
Experiments have shown that these mutations severely disrupt the reproductive behavior of zebrafish. Usually the males and females of these fish, ready to be fertilized, begin the courtship ritual a few minutes later after being placed in a single aquarium. However, the mutant species was not very interested in each other. To successfully spawn was only every tenth pair.
According to the authors, the main cause of reproductive failure the experimental fish was the lack of not secretogranin-2, and its derivative — secretoneurin. This peptide is a small fragment secretogranin-2, which is produced by the cutting enzymes. When the mutant individuals were administered a dose of secretoneurin, their reproductive behavior is partially recovered.
Thus, the team was able to confirm that secretoneurin is a previously unknown hormone. Rather, it affects the cells of the pituitary gland, stimulating the release of other hormones.
Secretoneurin not specific to a fish — like compounds produced in the body of other vertebrates, including humans. This gives hope that the opening will find wide application: from the regulation of spawning have grown in captivity fish to create new tools against infertility in humans.
Experiments with zebrafish made it possible to describe a neural network which is responsible for the sideline — one of the most important sensory organs of fish and amphibians. It turned out that the contained cells are localized in specific brain regions and evenly distributed on it. The majority of neurons responds to flow from head to tail.