Evaluation of Analgesic Activity of Papaver libanoticum Extract in Mice: Involvement of Opioids Receptors

Abstract

Papaver libanoticum is an endemic plant to Lebanese region (family Papaveraceae) that has not been investigated before. The present study aimed to explore the analgesic activity of dried ethanolic extract of Papaver libanoticum (PLE) using tail flick, hot plate, and acetic acid induced writhing models in mice. The involvement of opioid receptors in the analgesic mechanism was investigated using naloxone antagonism. Results demonstrated that PLE exhibited a potent dose dependent analgesic activity in all tested models for analgesia. The analgesic effect involved activation of opioid receptors in the central nervous system, where both spinal and supraspinal components might be involved. The time course for analgesia revealed maximum activity after three hours in both tail flick and hot plate methods, which was prolonged to 24 hours. Metabolites of PLE could be responsible for activation of opioid receptors. The EC50 of PLE was 79 and 50 mg/kg in tail flick and hot plate tests, respectively. The total coverage of analgesia by PLE was double that of morphine in both tests. In conclusion, PLE proved to have opioid agonistic activity with a novel feature of slow and prolonged effect. The present study could add a potential tool in the armaments of opioid drugs as a natural potent analgesic and for treatment of opioid withdrawal syndrome.

Figure 1

Effect of different doses of PLE on change in latency time using tail flick test in mice.

Figure 2

Relative activity of PLE with respect to morphine in tail flick method.

Figure 3

Effect of different doses of PLE on change in latency time using hot plate test in mice.

Figure 4

Relative activity of PLE with respect to morphine in hot plate method.

Figure 5

Effect of naloxone on latency time change in tail flick test in mice.

Figure 6

Effect of naloxone on latency time change in hot plate test in mice.

Figure 7

DRC of PLE in tail flick (a) and hot plate (b) tests in mice.

Figure 8

Percentage of inhibition of abdominal contractions in acetic acid induced writhing in mice.