Effect of long-term administration of metanil yellow on the structure of cerebellar cortex of adult male albino rat and the possible protective role of anise oil: A histological and immunohistochemical study

Introduction: Metanil yellow is used as a colorant in many food processing industries. It has toxic effects on some organs in humans and animals. Anise oil, an essential oil of the flowering plant Pimpinella anisum L., possesses a wide range of pharmacological activities and a proposed role in combating some neurological disorders.
ِِِAim: To study the effect of long term administration of metanil yellow on the structure of cerebellar cortex of adult male Albino rats and to evaluate the possible protective role of anise oil.
Materials and Methods: Forty-five adult male albino rats were divided into four groups; Group I (control), group II further divided into two subgroups (a and b) that received anise oil (0.5ml/kg) orally for four and eight weeks, respectively., Group III also divided into two subgroups (a and b) orally administered metanil yellow (200 mg/kg) for four and eight weeks, respectively. Alike, group IV divided into subgroups (a and b) received both anise oil and metanil yellow at the same dose, route and duration as in groups II and III, respectively. Specimens from the cerebellar cortex were processed for light microscopy. Immunohistochemical study was carried out using antibodies against active caspase-3 and glial fibrillary acidic protein (GFAP).
Results: Specimens from metanil yellow-treated animals showed a high significant decrease in the mean number of Purkinje cells, which appeared shrunken, distorted and surrounded by large vacuolar spaces. Some of their nuclei were shrunken and deeply stained, while others were fragmented. The molecular and granular layers displayed prominent perineuronal spaces. Immunohistochemically, highly significant increases in active caspase-3 and GFAP immunoreactions were observed. In contrast, minimal changes were observed in rats treated concomitantly with metanil yellow and anise oil.
Conclusion: Metanil yellow-induced structural changes in cerebellar cortex of adult rat that could be ameliorated by concomitant treatment with anise oil.