ANTINOCICEPTIVE EFFECT OF THE HYDROALCOHOLIC EXTRACT OF BAUHINIA SPLENDENS STEMS IN MICE

The analgesic effect of the hydroalcoholic extract of the stems of Bau hinia splendens (Leguminosae) has been investigated in chemical and th ermal models of nociception in mice. The hydroalcoholic extract of B. splendens, 3-60 mg kg(-1) intraperitoneally or 50-400 mg kg(-1) orally , caused dose-related, and long-lasting (up to 3 h) inhibition of acet ic acid-induced abdominal constriction in mice, with ID50 values of 3. 2 and 177.6 mg kg(-1) and maximum inhibition of 95+/-2 and 61+/-6%, re spectively; In the formalin test, the extract given intraperitoneally (1-60 mg kg(-1)) or orally (50-400 mg kg(-1)) caused graded inhibition of both phases of formalin-induced pain, being about 5- to 6-fold mor e potent in attenuating the second phase of pain. The calculated mean ID50 values for the first and the second phases were 11.5 and 2.5 mg k g(-1), respectively, for intraperitoneal administration and >200 and 7 0 mg kg(-1), respectively, for oral administration; the percentages of maximum inhibition for the first and the second phases were 68+/-6 an d 99+/-1, respectively, for intraperitoneal administration and 37+/-6 and 69+/-9, respectively, for oral administration. However, at the sam e doses the extract did not significantly affect the oedematogenic res ponse induced by formalin. The treatment of animals with naloxone (5 m g kg(-1), i.p.) completely reversed the analgesic effect caused by mor phine (5 mg kg(-1), s.c.), but had no effect against the antinocicepti ve effect of the hydroalcoholic extract of B. splendens (60 mg kg(-1), i.p.) when assessed against acetic acid-induced abdominal constrictio ns. Furthermore, the extract, in contrast with morphine, had no analge sic effect in the hot-plate test. These data show that the hydroalcoho lic extract of B. splendens has significant analgesic action when asse ssed against several models of pain. The mechanism underlying its anal gesic effect still remains unknown, but seems to be unrelated to inter action with opioid systems.