Abstract. The effect of benzodiazepine anxiolytic diazepam in Danio rerio was investigated. Methods. A stress test on novelty situation was used: a fish was placed first in a beaker with a dissolved pharmacological substance (or water) and then into a novel tank for 6 min, where the trajectory, the path length, the number of movements to the upper part of the novel tank, the number and time of the pattern of freezing of the experiment were measured. Results. In response to the novelty of tank, the fish was shown to react by submerging to the bottom, increasing the freezing, and reducing the number of movements to the upper half of the novel tank. After diazepam exposure (administration), the fish was not only in the lower, but also in the upper part of the novel tank. A pharmacological analysis of diazepam effect in Danio rerio showed that in a certain dose range of 110 mg/l anxiolytic reduces (in comparison with the control group of fish) the number and time of freezing, increases the number of movements in the upper half of the tank and the swimming time in upper part of the tank. Diazepam causes a disinhibition of motor activity at doses of 1 and 5 mg/l, which may be explained by the effect of small doses of tranquilizers on presynaptic GABA-A autoreceptors. Diazepam 20 mg/l has a depriving effect. Conclusion. Diazepam acts in a higher dose range (110 mg/l) than phenazepam (0.11 mg/l) in Danio rerio. At the same time, diazepam is characterized by a domed dose-dependent effect, in contrast to the action of phenazepam. The prospect of using Danio rerio as an animal model in behavioral pharmacology is not inferior to studies in rodents.
The aim: of the study was to investigate the level of ghrelin in various brain structures during a stress response in Zebrafish to a predator, to evaluate this indicator as a potential biomarker of stress, and the effect of a benzodiazepine tranquilizer (phenazepam) on stress-induced changes Materials and methods: The object of the study was Zebrafish, or Danio rerio wild type, which was subjected to stress by exposure to a predator Hypsophrys nicaraguensis from the cichlid family. In the tail tissue, the level of cortisol was determined, in the brain – the level of total (acylated and non-acylated) ghrelin by the method of enzyme-linked immunosorbent assay. The benzodiazepine anxiolytic phenazepam (1 mg/L), a ghrelin antagonist [D-Lys3]-GHRP-6 (0.333 mg/l) and corticotropin-releasing hormone (CRF; 0.4 mg/L) were used as the pharmacological agents. Results and discussion: Exposure to a predator, just as administering CRF, more than doubled the level of cortisol in the tail tissue. [D-Lys3]-GHRP-6 and phenazepam prevented an increase in a tissue cortisol level. Simultaneously, in the medulla oblongata and cerebellum, the phylogenetically most ancient structures, rather than in the forebrain (telencephalon) or in the midbrain (corpora bigemia), the level of ghrelin was recorded about 500 pg/g of total protein. In response to exposure to a predator, the level of ghrelin increased in the forebrain and midbrain to nanogram concentrations and moderately decreased in the cerebellum. The effect was prevented by phenazepam and [D-Lys3]-GHRP-6. Conclusion: Increases in ghrelin in the brain in response to stressful situations can be seen as a functional brain biomarker of stress, along with increased levels of tissue cortisol levels. Both of these effects are prevented by both the ghrelin antagonist and the benzodiazepine tranquilizer. The mechanism of action of the tranquilizer is a functional antagonism between the GABAergic system of the brain and the ghrelin system.
BACKGROUND: Previously has been shown that fish kisspeptin 1 (Kiss1) acts on the brains serotonin system to reduce anxiety-phobic reactions in Danio rerio. The kissspeptin gene (kiss1) of teleost fish is also a conservative orthologue of the kissspeptin gene (KISS1/Kiss1) of mammals. AIM: In this work we investigated the possible anxiolytic effect of mammalian kisspeptin analogs Kiss1 in Danio rerio in comparison with antidepressants of the serotonin-type of action. MATERIALS AND METHODS: A novelty test was used: the fish was first placed in a beaker with a dissolved pharmacological substance (or H2O), and then in a viewing tank for 6 min, where the trajectory of movement, the length of the path, the number of movements to the upper part of the tank, the time spent in the lower part of the tank, number and time of the freezing were automatically recorded. RESULTS: It is shown that, in response to the novelty of being placed in a viewing tank, fish react by moving to the bottom, increasing friezing, and reducing the number of movements to the upper half of the tank. Against the background of antidepressants clomipramine, paroxetine or trazodone (0.51 mg per 1 l of water), the fish were not only in the lower, but also in the upper part of the viewing tank. The average path length did not change significantly. The time in the lower part of the tank decreased by more than 2 times compared with the control group of animals and showed a dose-dependent effect. The number of movements to the upper part of the tank per experience increased significantly. Mammalian kisspeptin analogues Cloud Clone (USA) in a dose 0.011 mg per 1 l of water caused a similar patterns of behavior in fish in response to novelty. At the same time, the effects of kisspeptin analogs were lower than those of antidepressants. The most effective dose for the action of the studied kisspeptin analogs was 0.1 mg per 1 l of water. CONCLUSIONS: Thus, mammalian kisspeptin analogs Kiss1 reduce anxiety-phobic responses to novelty in Danio rerio. Data on the unidirectional effects of mammalian kisspeptin analogs and serotonin-type antidepressants support the potential role of Kiss1 in modulating serotonin-dependent behaviours in Danio rerio. The data obtained support the hypothesis that kisspeptin may be involved in the regulation of anxiety-phobic states, apparently to maintain the emotional aspects of reproductive behavior, such as sexual motivation and arousal.
We studied the effect of benzodiazepine anxiolytic phenazepam after the predator presentation to Danio rerio. The test of novelty was used: the fish was placed first in a beaker with a dissolved pharmacological substance (or H2O) and then into a novel tank for 6 min, where the trajectory, the path length, the number of movements to the upper part of the novel tank, the number and time of the pattern of freezing were measured. It is shown that, in response to the novelty of tank, the fish are reacted by submerging to the bottom, increasing the frizing, and reducing the number of movements to the upper half of the novel tank. After phenazepam administration, the fish were not only in the lower, but also in the upper part of the novel tank. The average path length did not change significantly in the range of doses used. The number and time of the frizing, as well as the time spent in the lower part of the novel tank, decreased more than 2 times compared to the control group of animals and showed a dose-dependent effect. The number of movements to the upper part of the novel tank for the experiment increased significantly from 1 in the control to 57 after phenazepam in a dose of 1 mg/l. At the same time, the number of movements of fish to the upper part of the novel tank significantly increased more than 2 times from 3th min of the experiment with the use of phenazepam in a dose of 1 mg/l. Predator presentation (Hypsophrys nicaraguensis) caused an increase in the number of freezing (temporary immobilization) and a decrease in the length of the trajectory of movement in the novel tank as compared with the Danio rerio control group. Phenazapam at a dose of 1 mg/l removed the effects of a predator, while exhibiting a typical effect: the number of movements to the upper part of the tank during the experiment significantly increased to 30; the time at the bottom of the tank was halved. It was concluded that the novelty stress test and the test with a predator are highly sensitive for studying anxiety-phobic reactions in Danio rerio.
Danio reriohas firmly established itself as a successful model for research in many areas of biology and medicine, first of all for developing new medicines. The aimof our study was to evaluate ghrelin level in zebrafish brain after stress and after phenazepam usage on stressed fish. Methods.In our study 96Danio rerio, predatorCichlasoma nicaraguensishave been used. The fish have been kept at anormal room temperature (2223C) with standard feeding time (twice per day). The level of neuropeptides has been tested by ELISA test. During experiment a fish has been firstly placed in a beaker with a dissolved pharmacological substance, then has been transferred into a tank with predator. In the end of experiment, it has been put into a novel tank for 6 min. The decapitation has been made. Thebrain has been divided into three anatomical parts:telencephalonjust behind the olfactory bulb, the middle partcorpora bigemiaandcerebellum, which is situated behind thecorpora bigemia. After that the material for ELISA test was made using GhrelinFISH, MyBioSource ELISA kit. Results.In the control group ghrelin has been determined only in thecerebellumin 57.14% of all fish. In the experiment with predator ghrelin has been found in all tested brain parts of fish, but in thetelencephalonthere was the highest level. Inthe experiment with phenazepam usage only and phenazepam administration after predator stress, the ghrelin value has not been determined atall. Conclusion.Thus we have found out that the ghrelin value increases after predator stress and the drug phenazepam eliminated it completely after its administration. We may suppose that the administration of anxiolytics such as phenazepam can reduce the anxiety inDanio rerio.
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