**2.1 Sildenafil citrate administration**

The rats in the treatment groups (A, B, & C) received respectively, 0.25mg/kg, 0.70mg/kg and 1.43mg/kg body weight of Sildenafil citrate base dissolved in distilled water daily for 6 weeks, through orogastric feeding tube, while that of the control group D, received equal volume of distilled water daily during the period of the experiment. The rats were sacrificed by cervical dislocation on day forty-three of the experiment. The liver and kidneys of the animals in each group were dissected out and quickly fixed in 10% formal saline for general histological studies.
