The changes of protein kinases activities in the brain structures after ghrelin antagonists administration in previously stressed Danio rerio

BACKGROUND: Nowadays there are a lot of data to suggest about an important role of ghrelin signaling system in stress response and reinforcement mechanisms. There is a common opinion that a protein kinase system plays a role of a second intracellular messenger for ghrelin system.

AIM: So, the aim of our study was to measure the total protein kinase activity in brain structures of Danio rerio. The all procedures have been approved according to the Local Ethical Committee of Institute of Experimental Medicine.

MATERIALS AND METHODS: In our study it has been used 50 specimen Danio rerio 6–8 months of age. There also has been used a predator (Hypsophrys nicaraguensis). During experiment a fish has been firstly placed into a tank of water with a dissolved pharmacological substance for 5 min, then has been transferred into a tank with predator also for 5 min. Two ghrelin antagonists have been used in our experiment in 0.333 mg/l dosage [D-Lys3]-GHRP-6 and Agrelax, a recombinant peptide analogue of ghrelin with molecular weight 3.5 kD, which has been invented in our Institute. The brain has been divided into three anatomical parts: telencephalon, midbrain and cerebellum. After that the material for kinase activity assay was made (ADP sensor Universal Kinase Activity Assay kit, BioVision).We also have used GraphPad Prism 6 for statistical estimation. Kolmogorov–Smirnov test Mann–Whitney U-test have been used as statistical tests.

RESULTS: In control group, the kinase activity has been determined in all tested brain structures. After predator exposure, the kinase activity has significantly changed. After [D-Lys3]-GHRP-6 administration there has not been determined any protein kinase activity in all brain structures. In the cerebellum the kinase activity has been the highest after Agrelax administration. Protein kinase system demonstrates significant stress response.

CONCLUSIONS. Pharmacological action on ghrelin receptors leads to changes in kinase system in Danio rerio’s brain structures.