Zeatin, an adenine-derivative cytokinin has well-established functions in plants. It is also suggested to activate A2A receptors in animals, however, there is limited knowledge of its effects. The main objective of this study is to evaluate the possible effects of zeatin on depression, and our hypothesis is that zeatin might induce an anti-depressant effect via A2A receptor-linked pathways. The forced swim test was used to create a depression-like model on female and male rats. A balanced zeatin isomer mixture (80 % trans-zeatin (tZ), 20 % cis-zeatin (cZ)) was administered intraperitoneally to analyze the effects. Caffeine with a suboptimal dose (2 mg/kg) was used as a known ligand of A2A receptor. Finally, a molecular docking study was also implemented to compare caffeine and tZ in the ligand binding site of A2A receptor. We demonstrate that (1) there is a clear sex-dependent difference in the susceptibility to depression-like symptoms, where female rats in the metestrus phase display higher depressive-like behavior and lower responses to the anti-depressant-like effects of pharmacological applications; (2) 10 mg/kg zeatin exerts an anti-depressant-like effect for both females and males without affecting locomotor activity; (3) 8 mg/kg tZ alone replicates this effect for both sexes, (4) the effect of zeatin is also differential for either sex and (5) the similar effect of caffeine and zeatin implies that the effect might be exerted via A2A receptor mediated pathways. Computational analysis further yielded similar binding patterns for both ligands. In conclusion, zeatin might have a potential therapeutic use in depression, acting via adenosinergic pathways.
Keywords: A2A receptor; Caffeine; Depression; Forced swim test; Zeatin.
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