Antinociceptive activity of methanol extract of leaves of Solanum sisymbriifolium in heat and chemical-induced pain

Solanum sisymbriifolium Lamk. (Solanaceae) is a perennial prickly herb traditionally used in folk medicine to treat different ailments. This study evaluated the methanol extract of S. sisymbriifolium leaf (MSS) (100, 200, and 400 mg/kg; p.o.) for analgesic activity using heat- and chemical-induced pain models such as hot plate, tail immersion, formalin-induced licking and acetic acid-induced writhing. Interaction with the opioid receptor system was verified using naloxone to antagonize the effect of MSS, if any. MSS demonstrated significant and dose-dependent antinociceptive activity, though moderate, in both hot plate and tail immersion test (p < 0.05). Naloxone reversed the antinociceptive effect in both tests. MSS produced profound antinociceptive effect in formalin test and acetic acid-induced writhing at 400 mg/kg dose. These results imply that the antinociceptive effect of MSS is mainly due to its central effect and peripheral effects also contribute to some extent. These results provide preliminary evidence of antinociceptive activity of S. sisymbriifolium leaves and the potential of the plant in treating different painful conditions.