EVALUATION OF THE EFFECTS OF AQUEOUS EXTRACT OF Psidium guajava LEAVES ON LEAD ACETATE-INDUCED NEUROTOXICITY IN ADULT WISTAR RATS

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Department of Medicine

ABSTRACT
Lead poisoning is known to cause a number of adverse effects including brain damage, mental impairment and severe behavioural anomalies, impaired cognitive functions in human and experimental animals. The toxic effects of lead are treated by chelation therapy which also depletes the body store of essential cations and as such there is need to look for alternative therapy to lead poisoning. The present study was aimed at evaluating the effects of aqueous extract of Psidium guajava leaves (EAPG) on lead acetate induced changes in behaviour, cerebellum, cerebrum and hippocampus of adult Wistar rats. Thirty five (35) adult male Wistar rats were divided into 7 Groups of 5 rats per group. The rats were trained for spatial learning and memory, and motor activity using Morris water maze and beam Balance methods, respectively. Group 1 was administered with distilled water from 1st to 35th day, Group 2 was administered with 1000 mg/kg body weight (bwt) of EAPG only from 1st to 35th day, Groups 3 to 7 were administered with 120 mg/kg bwt of lead acetate from 1st to 21st. While the rats in Group 3 were sacrificed at the 22nd day of the administration, Group 4 was administered with distilled water from the 22nd to 35th day, Group 5 was treated with 500 mg/kg bwt of EAPG from the 22nd to 35th day, Group 6 was treated with 1000 mg/kg bwt of EAPG from the 22nd to 35th day and Group 7 was treated with 10 mg/kg bwt of Succimer from 22nd to 35th day. The administrations were carried out orally once per day for 35 days. The rats were sacrificed and blood samples were collected via cardiac puncture for haematological and biochemical analysis. Brain tissues were removed and fixed in Bouin?s fluid and processed for histopathological studies using Haematoxyline and Eosin (H and E), and Cresyl Echt Violet stains. The results showed that there were significant deficits in spatial learning, memory and motor activities in rats exposed to lead acetate when compared with the control rats and those xviii exposed to lead acetate and treated with EAPG (P < 0.05). Oxidative stress was induced in rats exposed to lead acetate by increasing lipid peroxidation and decreasing catalase, superoxide dismutase and reduced glutathione, and the effects were reversed in lead exposed rats treated with EAPG. There were changes in haematological indices of rats exposed to lead acetate and these changes were reversed in rats treated with EAPG. The study also revealed histopathological changes in hippocampus, cerebellar and cerebral cortices of rats exposed to lead acetate and the changes were ameliorated when treated with EAPG. Thus, the present study has established that aqueous extract of Psidium guajava leaves at doses of 500 mg/kg bwt and 1000 mg/kg bwt was able to ameliorate the effects of lead acetate induced toxicity and may likely be beneficial to the population in endemic areas that are exposed to lead poisoning.