Evaluation of protective effects of non-selective cannabinoid receptor agonist WIN 55,212-2 against the nitroglycerine-induced acute and chronic animal models of migraine: A mechanistic study.

Migraine is a neurological debilitating disorder. Previous studies have shown that cannabinoid receptor agonists have analgesic effects in various models of pain. In this study, therefore, we investigated anti-nociceptive effects of WIN 55,212-2, and the role of either CB₁ or CB₂ receptors in nitroglycerine (NTG)-induced animal model of migraine.

The present study was conducted on both male and female rats receiving NTG (10 mg/kg, i.p.) to induce acute (single dose of NTG) and chronic (repetitive doses of NTG) models of migraine. Additionally, three groups received WIN 55,212-2 (0.33, 1, 3 mg/kg, i.p.) 45 min before behavioral tests. Additionally, AM251 and AM630 (CB₁ and CB₂ receptor antagonist, respectively, 1 mg/kg, i.p.) were used to evaluate the possible involvement of CB1 and CB2 receptors during the protective effects of WIN 55,212-2.

We found that NTG (10 mg/kg, i.p.) in both acute and chronic models increased sensitivity to pain. In acute model, we found that WIN 55,212-2 (almost high doses) decreases the level of pain mainly through CB₁ receptor due to CB₁ antagonist abrogates its protective effects, however, in formalin test CB₂ receptors also had crucial roles in both phases at 3 mg/kg of WIN 55,212-2. In chronic model, WIN 55,212-2 (0.33, 1 and 3 mg/kg) significantly attenuated NTG-induced hyperalgesia through both CB₁ and CB₂ receptors.

Our data supported the argument that activation of CB₁ and CB₂ receptors by WIN 55,212-2 may be considered a new medication for migraine, however in lack of each receptor leads to different responses from deletion to the reduction of analgesic effects.