Antinociceptive activity of aerial parts of Polygonatum verticillatum: attenuation of both peripheral and central pain mediators.

Polygonatum verticillatum All. is used traditionally as an analgesic and plant diuretic. The methanol extract of aerial parts of Polygonatum verticillatum (PA) was assessed in various experimental paradigms. The pain threshold in the form of abdominal constriction induced by acetic acid was significantly (p < 0.01) inhibited by PA at test doses (50, 100 and 200 mg/kg). In the formalin test, PA elicited a significant (p < 0.01) analgesic activity in both phases and strongly attenuated the formalin-induced flinching behaviour. The hot plate test was used to evaluate central involvement in the analgesic profile of PA. The PA significantly relieved thermal-induced pain. From a mechanistic point of view, the central antihyperalgesic activity was tested for antagonism with naloxone, but no antagonism was observed. The current investigations suggest that the active constituent(s) in PA has an analgesic profile with predominant peripheral activity which is augmented by an opioid independent central effect. In the diuretic assay, PA (300 and 600 mg/kg) showed mild insignificant diuretic activity. Our study rationalized the traditional use of Polygonatum verticillatum in the treatment of painful conditions.