Effects of diphenylhydantoin on locomotion and thigmotaxis of larval zebrafish

Antiepileptic effects of diphenylhydantoin (DPH) have been documented in animal studies and clinical research, while little is known about the effects of the drug on basic behaviors and anxiety-related behaviors. In order to understand neuroactivities of DPH deeply and administrate DPH in clinic rationally, it is necessary to study neurobehavioral effects of the drug. In the present study, the effects of DPH on the locomotor activity and thigmotaxis of zebrafish larvae at 5 days post fertilization (dpf) were explored under different illumination conditions. The influence of DPH on zebrafish larval responses to visual stimuli (sudden illumination transition from light to dark) was also investigated. Under light or dark condition, exposure to high concentrations of DPH resulted in decreased locomotor activity and thigmotaxis, whereas DPH treatment at low doses enhanced the locomotor activity. Additionally, sudden illumination transition induced robust increase in the locomotor activity and this phenomenon was not modified by DPH treatment. Our results suggest that DPH has potential stimulatory and inhibitory effects on the locomotor activity and possesses anxiolytic properties. In addition, responses of 5-dpf zebrafish larvae to visual stimuli were not modified by DPH treatment.