ABSTRACT
The bark of the West African Pausinystalia yohimbe tree is a traditional aphrodisiac and the source of yohimbine, a prescription drug for impotence. It appears to be modestly effective, but it also presents numerous safety risks. The possible side effect on the haematological parameters and histology of the hypothalamus has not been considered. This study investigated experimentally using adult male Wistar rats, the changes in haematological parameters and the histology of the hypothalamus due to oral administration of the crude extract Pausinystalia yohimbe bark. Thirty six (36) adult male Wistar rats of average weight of 200g, used for this experiment. The animals were grouped into four (4) groups of nine (9) animals per group. With group I serving as the control and administered distilled water. While group II, III and IV administered 30mg/kg, 50mg/kg and 100mg/kg body weight per day of the crude extract of Pausinystalia yohimbe bark orally respectively, for three (3) weeks. Blood samples were collected from all the animals for the haematological studies and the brain tissues were also collected and fixed in Bouin's fluid and processed for histological studies using the method of Glee's. The photomicrographs of the tissues were taken using an Optical Eye Piece connected to a computer system. The results showed that the Pausinystalia yohimbe bark extract produced significant increased in the erythrocytes count values, total protein and clothing time decrease in the leukocyte count, monocyte and eosinophils differential counts. The extract also has excitatory effect on the nuclei of the hypothalamus, indicating cellular hyperplasia.