Morphine-induced Cognitive Dysfunction Model in Zebrafish

The neural pathway of opioid use plays a crucial role in drug abuse, cognitive alteration, and abnormal change in neurobehavior. This study aims to investigate the effect of morphine on changes in cognitive aspect through assessment of the startle habituation response in the zebrafish model. Zebrafish embryos were exposed to 0.8 μM morphine for 5 days, starting from 5-hour post-fertilisation (hpf). On 6-day post-fertilisation (dpf), the larvae were transferred to the custom startle apparatus for assessment. The recorded videos were analysed using Toxtrac software. From the analysis, morphine-treated larvae showed impairment in the habituation response, with excessive startle response and non-consistent decrement in habituation. Besides, chaotic movements and preference towards peripheral zone in the larvae treated with morphine also signifying anxiety. We postulate that the morphine regulated pathway are involved in the cognitive alteration and abnormal behaviour of morphine-treated zebrafish. Future studies are required to associate the morphine-induced behaviour to the neural circuitry and firing activities.