Antinociceptive and antidepressant like effects of Securidaca longepedunculata root extract in mice

The aqueous root extract of Securidaca longepedunculata (polygalaceae) was investigated for possible antinociceptive and central nervous system (CNS) effects in mice. Three nociceptive models; acetic acid, formalin and tail-flick tests were used to study the antinociceptive activity. Rectal temperature test was employed as an adjunct to the nociceptive models. The extract at 200 and 400 mg/kg significantly and dose dependently reduced the nociception induced by the acetic acid and in the early phase of formalin test (P<0.05). The extract exerted significant (P<0.05) hypothermic effect in the 15 and 30 min of the rectal temperature test. The antinociceptive and hypothermic effects were partially reversed by naloxone (1mg/kg). The tail-flick test produced an insignificant increase in tail-flick latency at 400 mg/kg after 60 min of the test, but significantly (P<0.05) increase tail-flick latency in the 400mg/kg group of animals pre-treated with naloxone (1 mg/kg) after 120 min of the test. The extract also produced a significant (P<0.05) naloxone reversible antidepressant like effect in the forced swimming test (an animal model of depression). Collectively, these results suggest that the extract possess antinociceptive and antidepressant like effects with possible involvement of opioidergic pathways. The extract at limit dose of 2 g/kg body weight appeared to be safe in oral formulation.