Study of the effects of kisspeptin analogs on the behavior of Danio rerio

BACKGROUND: This study aims to analyze the behavioral effects of mammalian Kiss1 kisspeptin analogs, Clone (USA): KS4, KS5, KS6, KS7, KS8, KS9, and Kiss10, on Danio rerio (zebrafish). The peptides have structural variations in the final four amino acids.

MATERIALS AND METHODS: Kisspeptins were dissolved in aquarium water and administered in two doses: 1) 0.01 mg per 1000 ml of water, and 2) 0.1 mg per 1000 ml of water. Phenazepam, an anxiolytic, was also dissolved in water and used in three doses: 1) 0.1 mg per 1000 ml, 2) 0.5 mg per 1000 ml, and 3) 1 mg per 1000 ml. The study compared kisspeptines with anxiolytics using phenazepam as an example in the novelty test. The fish’s response to novelty in the viewing tank was assessed, including diving to the bottom, increased freezing, and decreased movement in the upper half of the tank. Fish residence time in the lower part of the tank after phenazepam administration decreased, especially at a dose of 0.5 and 1 mg/l.

RESULTS: Kisspeptin analogues decreased the indices characterizing the anxious state of the fish. Against the background of Kiss1 kisspeptin analogues, the average fish path length differed significantly in contrast to the effects of phenazepam. KS4 at a dose of 0.1 mg/l showed a 1.4-fold decrease in the number of freezing, in the freezing time, in the trajectory length and 1.5-fold increase in the number of transitions to the upper part of the tank. The dose of 0.01 mg/l decreased the number of freezing, freezing time, and trajectory length by 1,5-3 times. KS5 at a dose of 0.1 mg/l decreased the number of freezing, the freezing time, the trajectory length and the number of transitions to the upper part of the tank by 1.2–1.6 times. The dose of 0.01 mg/l decreased the number of freezing, freezing time, trajectory length by 2.8–3 times. KS6 at a dose of 0.1 mg/l decreased the number of freezing, the freezing time, and the trajectory length by 2–2.5 times. The number of transitions to the upper part of the aquarium increased 2.5 times. The dose of 0.01 mg/ml decreased the number of freezing, freezing time, and trajectory length by 1.7–2.2 times. KS7 at a dose of 0.1 mg/l decreased the number of freezing, freezing time, and trajectory length by 1.3–2 times. The number of movements to the top of the aquarium increased 1.6-fold. The dose of 0.01 mg/l decreased the number of freezing, freezing time, trajectory length by 1.6 times. KS8 at a dose of 0.1 mg/l decreased the number of freezing, the freezing time, and the trajectory length by 1.6 times. The dose of 0.01 mg/l decreased the number of freezing, the freezing time, and the trajectory length by 1.8–2.3 times. KS9 at a dose of 0.1 mg/l decreased the number of freezing, the freezing time, and the trajectory length by 1.2–2 times. The dose of 0.01 mg/l reduced the number of freezing, the freezing time, and the trajectory length by 1.6 times. In Kiss10 at a dose of 0.1 mg/l, there was a 1.4–1.6-fold decrease in the number of freezing, in freezing time, and in trajectory length. There was a 2.7-fold increase in the transitions to the upper part of the aquarium. The dose of 0.01 mg/l decreased the number of freezing, freezing time, and trajectory length by 1.3–1.7 times. We observed a 1.3-fold increase in the number of trajectories. Summarizing the obtained indicators, we came to the conclusion that kisspeptin analogues were not inferior in their effect to the effects obtained after taking the tranquilizer phenazepam. Among mammalian kisspeptin analogues, KS6 at a dose of 0.1 mg/L showed the best performance.

CONCLUSIONS: The study concludes that mammalian Kiss1 kisspeptin analogs and Kiss10 reduce anxiety-phobic reactions to novelty in Danio rerio. The effects of the studied kisspeptin analogs are lower than those of phenazepam. Kisspeptin is involved not only in the modulation of serotonin-dependent behavior in Danio rerio but also in the GABA-ergic system, resembling benzodiazepine-type tranquilizers. The results support the hypothesis that kisspeptin may be involved in the regulation of anxiety-phobic states, likely playing a role in maintaining the emotional aspects of reproductive behavior, such as sexual motivation and arousal.