MATHIAS OGHENOR

This study evaluated the neurotoxic effects of long-term exposure to N-(1,3-dimethylbutyl)- N′-phenyl-p-phenylenediamine quinone (6PPDQ), a transformation product of the tire additive 6PPD, on the brain of Clarias gariepinus juveniles. The research, motivated by growing concern over tire-derived contaminants, aimed to determine the effects of 6PPDQ on acetylcholinesterase (AChE) activity, acetylcholine (ACh) levels, and brain histology. A total of 237 fish were exposed to 500 µg/L, 1,000 µg/L, and 1,500 µg/L of 6PPDQ for 28 days under laboratory conditions, following OECD sub-lethal toxicity guidelines. AChE activity was determined using Ellman’s spectrophotometric method, while histopathological alterations in the telencephalon and optic tectum were assessed with haematoxylin and eosin (H&E) staining. Results revealed a significant (p < 0.05) dose- and time-dependent inhibition of AChE activity with a corresponding increase in ACh concentration. Histological analysis showed neuronal shrinkage, vacuolation, pyknosis, and mild gliosis in exposed fish, indicating oxidative stress and neuroinflammatory responses. The study concludes that prolonged exposure to 6PPDQ disrupts cholinergic neurotransmission and alters brain histoarchitecture in C. gariepinus. These findings highlight the ecological risks of tire-derived pollutants and emphasize the need for environmental monitoring and stricter regulation to mitigate their impact on aquatic life and ecosystem health.