THE EFFECTS OF ETHANOLIC STEM EXTRACT OF UVARIA CHAMAE ON MERCURY CHLORIDE - INDUCED NEUROTOXICITY IN THE PREFRONTAL CORTEX OF ADULT WISTAR RATS

ABSTRACT Mercuric chloride (HgCl₂) is a potent environmental neurotoxin known to induce oxidative stress, neuroinflammation, and structural damage within higher cortical regions of the brain. This study investigated the neuroprotective effects of Uvaria chamae root extract on mercuric chloride-induced neurotoxicity in the prefrontal cortex of adult Wistar rats. Thirty animals were randomly divided into control and experimental groups, including HgCl₂-treated, extract-treated, and co-treated groups. Neurobehavioural performance was assessed using the Y-maze test for spatial working memory, the Morris Water Maze for learning and memory retention, and the Open Field Test for exploratory behaviour and anxiety indices. Biochemical assays were carried out to quantify oxidative stress biomarkers, including malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT). Histological examination of the prefrontal cortex was performed to evaluate cytoarchitectural integrity. HgCl₂ exposure resulted in significant behavioural deficits, as evidenced by reduced spontaneous alternation in the Y-maze, prolonged escape latency in the Morris Water Maze, and decreased exploratory activity in the Open Field Test. Biochemically, HgCl₂ markedly increased MDA levels while reducing SOD and CAT activities, indicating elevated oxidative stress. Histological findings revealed neuronal degeneration, vacuolation, and disrupted cortical layering within the prefrontal cortex. Co-administration of Uvaria chamae extract ameliorated these alterations, improving behavioural performance, restoring antioxidant enzyme levels, and preserving cortical morphology. Animals treated with the extract showed reduced neurodegeneration and improved neuronal arrangement compared to the HgCl₂-only group. Overall, the findings demonstrate that Uvaria chamae root extract possesses significant neuroprotective properties against mercuric-induced cortical damage, likely mediated through its antioxidant and cytoprotective mechanisms. This study provides scientific support for the ethnomedicinal use of Uvaria chamae and suggests its therapeutic potential in mitigating heavy metal-induced neurotoxicity. keywords: Uvaria chamae, mercury chloride, prefrontal cortex, oxidative stress, neuroprotection, Wistar rats