Antinociceptive effects of essential oil of Salvia hypoleuca L. in mice

Pain is a sensorial modality, which in many cases represents the only symptom for the diagnosis of several diseases. It often has a protective function. Although morphine has reigned for centuries as the king of painkillers, its rule hasn’t been totally benign. There are concerns about its addictive properties and side effects, which include respiratory depression, drowsiness, decreased gastrointestinal motility, nausea and several alterations of the endocrine and autonomic nervous systems. Since the plant is being used traditionally in the treatment of painful illnesses, it would be worthwhile to evaluate its antinociceptive activities in mice. The objective of the present work is to evaluate the analgesic effect of ethanolic extracts of Salvia hypoleuca leaves by formalin-test in mice. The ethanolic extracts and morphine were injected intraperitoneally. The control groups were administered saline as vehicles of ethanolic extract. Thirty minutes after the injection, pain scores were recorded for each group of mice by using an observational scale. The results showed that the ethanolic extracts of the plant, compared to normal saline, decreased pain scores for both the first phase (p<0.001 for all doses) and the second phase of pain (p<0.001 for doses 100mg/kg and 200mg/kg p<0.01 for dose 50mg/kg). Also, the LD50 of the ethanolic extracts of the plant were measured to be 7000mg per kg of body weight. The data indicate that this plant has analgesic effects on mice and the plant should be considered in future therapeutic researches.