Antinociceptive effect of the ethanol extract of the stem bark of <em>Musanga cecropioides</em> in mice

Abstract

Musanga cecropioides R. Apud Tedlie (Cecropiaceae), also known as umbrella tree is one of the medicinal plants used in Nigeria for pain and inflammation. The stem bark was extracted with absolute ethanol and screened for analgesic activities. The screening for analgesic properties was done using: acetic acid induced writhing; formalin induced pain, tail immersion and hot plate methods all in mice. Mice were divided into five groups of five each. The first group in all models served as control and received normal saline (0.9 % NaCl), the next three groups received either 50 or 100, 200 and 400 mg/kg of the extract. The 5^th group was given a reference drug either pentazocine (10 mg/kg) or aspirin (100 mg/kg). The extract at 50,100 and 200 mg/kg showed a dose dependent significant reduction of the number of writhes (p<0.05, p<0.05 and p<0.0001 respectively) compared with the control. The extract also showed a non-dose dependent significant reduction of the paw licking time in the formalin-induced pain test with more prominence in the second phase. A significant increase in the mean reaction time of mice in the tail immersion and hot plate tests (p<0.0001) was also produced by the extract in comparison with the control. This effect however was not dose dependent. The results suggest that the plant has significant peripheral and central analgesic effects, which may not be dependent on dose. Inhibition of the synthesis of prostaglandins may account for its peripheral analgesic effect, while its action on central receptors may account for its central analgesic activities.