The evolutionarily conserved role of melatonin in CNS disorders and behavioral regulation: Translational lessons from zebrafish

•Melatonin is an important brain hormone regulating circadian rhythm, neuroprotection and neuroimmune interactions.•Zebrafish (Danio rerio) is increasingly used in biomedical and neuroscience research.•Mounting evidence implicating melatonin in brain disorders and behavior.•Animal models are becoming a valuable tool to study neurobiology of melatonin.