Antinociceptive Effects of Ethanolic Extract of Salvia aethiopis in NMRI Mice

Herbal medicine has been used to relieve pain around the world for many years. The aim of this study was to evaluate the analgesic effect of ethanol extract on the aerial parts of Salvia aethiopis in NMRI mice. In the present experimental study, 126 mice (NMRI) were randomly selected and used for formalin, hot plate and acetic acid test. In every experiment there were seven groups of six mice.The rats were administrated with Salvia aethiopis extract at concentrations of (1, 10, 50 and 100 mg/kg body wt.) or morphine at concentration of (10 mg/kg body wt.) as the standard drug. The intact animals were used as controls and the control group was treated with saline. In the formalin test, formalin was injected into the dorsal surface of the right paw. The animals were observed for 45 min after injection of formalin and pain scores were recorded. After formalin injection, the pain rated from 0 to 5 min (early phase) and 15-45 min (second phase) were counted. In hot plate test, rats were placed on an aluminum hot plate kept at a temperature of 55 ± 0.5°C for a maximum time of 30 s. Reaction time was recorded when the animals licked their fore and hind paws and jumped at 0 and 15, 30, 45 and 60 min after intraperitoneal administration of the extract. In acetic acid experiment, the induced pain was counted by acetic acid administration. The number of abdominal constrictions induced by acetic acid were subsequently counted. The analgesic activity of the abdominal contractions were inhibited. The data were expressed as mean values ± SEM and tested, using analysis of one-way ANOVA test. The results showed that the extract decreased only the second phase of formalin-induced pain (p<0.05). the extract reduced the cramps induced by acetic acid (p<0.05). In the hot plate test, the ethanolic extract was able to increase the pain threshold during 60 min. The present data indicated that this plant had an antinociceptive effect on the mice, but more research is needed to clarify the mechanism of action of the analgesic effect of ethanolic extract of Salvia aethiopis.