Ameliorative Effects of Stachytarpheta jamaicensis Aqueous Leaf Extract on the Hippocampus and Prefrontal Cortex of N,N′-dimethyl-4,4′-bipyridinium dichloride-Induced Parkinson’s Disease in Adult Wistar Rats

Parkinson’s disease (PD) is the world’s second neurodegenerative disorder after Alzheimer’s dise-ase, and degeneration of dopaminergic neurons is the hallmark. This novel management approach for Parkinson’s disease with Stachytarpheta jamaic-ensis was to assess the role of leaf extract on the histological and morphological properties of the hippocampus and prefrontal cortex in Paraquat-induced Parkinson’s disease. Twenty-eight adult Wistar rats of both sexes (180 - 240g) were assigned to four groups: N,N′-dimethyl-4,4′-bipyridinium dichloride (Paraquat, P), Paraquat and Stachytarpheta jamaicensis (PSJ), only S. jamaicensis (SJ) and control (CTR). Animals were allowed water and food ad libitum throughout, and the weights were taken periodically. Parkinson’s-like disease was induced by intraperitoneal injection of 8.4 mg/kg body weight of Paraquat twice weekly for three weeks in the P and PSJ groups; The PSJ further received SJ aqueous leaf extract for another two weeks. Neurobehavioural assessment using Barnes maze for spatial learning and memory was carried out. Animals were sacrificed at the end of the experiment, and brain specimens were excised and processed for histological and biochemical analyses of the hippocampus and prefrontal cortex. The results showed that paraquat caused the degeneration of pyramidal and granular neurons, as well as dysfunctional output of the hippocampus and prefrontal cortex. There was a significant loss of dopaminergic neurons mainly in the P group. On the other hand, SJ leaf extract preserved most of the neurons. In conclusion, SJ leaf extract produced observable positive effects on the hippocampus and prefrontal cortex of the paraquat-induced Parkinson’s disease model.