Background and Objectives: One of the important objectives of physiological investigations is to find substances involved in pain relieving. This study investigated the effects of dietary virgin olive oil on acute and chronic pain and morphine analgesia in male mice using formalin test.

Materials & Methods: 24 male NMRI mice were randomly divided into 4 groups, 6 animals in each group (n = 6): 1) Sham group, consumption of standard diet during experiment, 2) Experimental group I, consumption of standard diet with olive oil but without receiving morphine, 3) Control group, consumption of standard diet and received morphine, and 4) Experimental group II, consumption of standard diet with olive oil and receiving morphine. Oral treatment period was 4 weeks. 10% olive virgin oil was added to standard diet, and morphine (10 mg/kg body weight), as standard drug, was injected subcutaneously. Pain was evaluated by using the formalin test.

Results: Oral administration of virgin olive oil could decrease neurogenic pain (the first phase of the formalin test) (p<0.001) and inflammatory pain (the second phase of the formalin test) (p<0.001). Furthermore, edible virgin olive oil somewhat increased the analgesic effect of morphine in the chronic pain phase significantly (p<0.001).

Conclusion: Oral administration of virgin olive oil has analgesic properties, and increases morphine’s analgesic effect. In fact, morphine in animals that have consumed edible virgin olive oil in their diet has more pain-relieving effect.

Keywords: Pain, Edible olive oil, Nociception, Morphine, Formalin test