Comparative evaluation of MPTP and rotenone as inducing agents for Parkinson's disease in adult zebrafish: Behavioural and histopathological insights

Parkinson's disease (PD), a prevalent neurodegenerative disorder, is marked by dopaminergic neuron loss and motor impairments. This study aimed to establish and compare PD models in adult zebrafish using two neurotoxins, MPTP and rotenone, evaluating their impact on behaviour and histopathology. Zebrafish were exposed to MPTP via intraperitoneal injection at two different doses or to rotenone in water for 21 days. Behavioural assessments, including Novel Tank Diving Test, bradykinesia, and C-bend response, revealed progressive motor and anxiety-like impairments, with rotenone exhibiting stronger locomotor effects. Histopathological analyses confirmed dose-dependent neurodegeneration in brain regions, with MPTP showing localized damage and rotenone causing widespread but milder effects. While both neurotoxins induced PD-like phenotypes, rotenone produced more pronounced locomotor deficits, whereas MPTP triggered anxiety-like symptoms. In conclusion, our study demonstrates that MPTP induces significant locomotor dysfunction along with anxiety-like symptoms, while rotenone strongly impacts locomotion with mild anxiety effects. Both neurotoxins exhibited maximum effects at their highest doses and over a similar time frame (Day 14 to Day 22). These findings highlight the distinct neurotoxic mechanisms of MPTP and rotenone and their relevance in modelling PD pathogenesis. The zebrafish model provides a robust platform for studying neurodegenerative diseases and testing therapeutic interventions. Further studies are required to explore the molecular mechanisms underlying their neurotoxic effects and to validate these models for long-term and translational research.