ABSTRACT
Nicotiana tabacum is the scientific name of the tobacco plant grown in several countries of the world. It has been used in variables ways such as smoking, snuffing, even chewing. The present study was to investigate the possible effects of aqueous and ethanolic leaf extracts of Nicotiana tabacum on the hippocampus, cerebral and cerebellar cortices of adult Wistar rats for a period of 21 days. Forty two adult Wistar rats of average weight of 150 g were used and were divided into 7 groups of 6 rats each (n = 6). The animals in Group 1 served as the Control and were given 0.2 ml of distilled water, Groups 2, 3 and 4 received 1000 mg/kg body weight, 500 mg/kg body weight and 250 mg/kg body weight respectively of aqueous extract of Nicotiana tabacum while, Groups 5, 6 and 7 received 1000 mg/kg body weight, 500 mg/kg body weight and 250 mg/kg body weight of ethanolic extract of Nicotiana tabacum respectively for 21 days via oral route once daily. At the end of the administration, the animals were then subjected to Morris Water Maze (MWM) and Beam Walking Test (BWT) and were humanely sacrificed on day 22 of the experiment and the brains were excised, fixed in Bouin's fluid and processed using Haematoxylin and Eosin (H&E) and Cresyl Fast Violet (CFV) staining technique. The result showed a significant decrease in the body weight in Groups 2 (139.50Â�69.59 g), 6 (145.67Â�19.40 g) and 7 (135.00Â�69.48 g) when compared to the Control Group (217.33Â� 15.87 g) (P< 0.05). The result showed that the mean latency time by rats to locate the platform after the administration of the extracts was increased in groups 6 (12.10Â�11.33 s) and 7 (12.65Â�8.83 s) when compared with the Control Group (11.69Â�11.08 s) though the increase observed was not significant. Oxidative stress markers were accessed in the brain and the result showed a significant decrease in CAT level in 2 (43.50Â�2.12 μg/ml), 4 (41.50Â�0.70 μg/ml), ix 5 (43.00Â�1.41 μg/ml), 6 (39.00Â�1.41 μg/ml) and 7 (36.00Â�1.41 μg/ml) (p<0.05) when compared with the Control (48.00Â�1.41 μg/ml). The result also showed a significant decrease in SOD level in 3 (2.10Â�0.14 nmol/ml), 5 (1.75Â�0.07 nmol/ml), 6 (1.90Â�0.01 nmol/ml) and 7 (1.70Â�0.14 nmol/ml) (p<0.05) when compared with the Control (2.45Â�0.21 nmol/ml). The result of the histological and histochemical examination of the hippocampus, cerebellar and cerebral cortices revealed degeneration in the brain. Cerebral and cerebellar cortices of treated rats with both extracts of Nicotiana tabacum revealed distortions such as pyknosis, karyorrhesis, vacuolations compared to the Control. Hippocampi of rats treated with both extracts revealed changes such as, irregular arrangement of CA3 hippocampal neurones and pyknosis when compared with the Control Group. The result from this study affirms that tobacco has effects on the brain and may induces neurotoxicity at various doses in Wistar rats. Therefore, suggests that the consumption of both form of Nicotiana tabacum may reduce body weight and alter the normal functions of the brain which may lead to brain dysfunction.