Abstract   

The aqueous extract of Ocimum gratissimum (Linn) leaves was investigated for its possible anti-nociceptive activity. The extract (100 - 800 mgkg’) in a dose - dependent fashion significantly (p < 0.005 and p < 0.0005) reduced the number of writhes and stretching induced by 0.6% aqueous solution of acetic acid in Wistar rats. At a higher dose of 800 mgkg the extract conferred 76.49% protection to the rats as compared with a low (100 mgkg dose which conferred 39.19% protection on the rats. The effect of the higher dose in protecting the rats against the acetic acid induced writhing was closer to that of the reference drug Pethidine hydrochloride at a dose of 20 mgkg In the acute toxicity studies, the aqueous extract did not cause any mortality up to a dose at lOg kg However, there were clinical signs of loss of appetite, decreased exploratory behaviour, and abnormal body posture.