Evaluation of Analgesic Effect of the Hydro-alcoholic Extract of Pycnocycla caespitosa in Comparison with Morphine and Aspirin by Formalin Test

The aim of this study was to evaluate the analgesic effect of the hydro-alcoholic extract of Pycnocycla caespitosa as a herbal medicine in comparison with morphine and aspirin.
Subjects and In this study male waster rats weighing in range of 170-200g were used. The hydro-alcoholic extract prepared by ethanol 70% (V/V) using maceration method. Animals divided into eight groups (n=6). The treatment groups received 200, 400, 600 and 800 mg/Kg extract, negative control group received 5ml/Kg normal saline, positive control groups received morphine (2.5mg/Kg) or aspirin (300mg/Kg) and last group received extract(600mg/Kg) and naloxone (1mg/Kg) intraperitonialy respectively After 30 min all groups received 50 μl formalin 2.5% in right hid paw subcutaneously and analgesia behaviors were scored.
Following administration of all doses of the extract produced analgesic effect at all periods of experiment except the first five min in comparison with negative control group. The most effective dose of extract (600mg/kg) and aspirin showed same analgesic effect in first phase of pain and there were no significant differences between extract with morphine and aspirin in phase 2 of pain. Naloxan only reduced the analgesic effect of extract in phase 2 of pain.
It can be concluded that extract may produce it’s analgesic effect through opioid receptors.