Acute alcohol exposure increases tyrosine hydroxylase protein expression and dopamine synthesis in zebrafish

Zebrafish have become a popular animal model for investigating the effects of alcohol on the brain and behaviour. Acute exposure to alcohol has been shown to alter dopaminergic signalling in zebrafish, but the underlying mechanisms have not been well defined. In the current study, we characterize the effects of alcohol on the zebrafish dopaminergic system by focusing on tyrosine hydroxylase, the rate-limiting enzyme in dopamine synthesis. Using western blot analysis, we demonstrate that a 60min exposure to 1% alcohol increases tyrosine hydroxylase protein expression in the zebrafish brain. Enzymatic activity assays confirmed that alcohol also increases tyrosine hydroxylase enzymatic activity, whereas HPLC analysis demonstrated increased levels of whole-brain dopamine and its metabolite DOPAC. In addition to activation of the dopaminergic system, behavioural analysis revealed accompanying increase of distance traveled following 1% alcohol exposure. These findings suggest that acute alcohol exposure elevates dopamine synthesis via increased tyrosine hydroxylase protein expression. Our results support the hypothesis that alcohol alters dopaminergic signalling in the zebrafish brain in a similar manner as compared to mammals.