Pre-emptive antinociceptive effects of a synthetic cannabinoid in a model of neuropathic pain.

The antinociceptive effects of WIN55,212-2, a synthetic cannabinoid, were evaluated in the model of partial sciatic nerve ligation after daily subcutaneous administration of 0.1 mg/kg a week before and two weeks after surgery. Mechanical allodynia and thermal hyperalgesia were evaluated in 46 rats allocated to receive: (1) Vehicle (before surgery)-Vehicle (after surgery); (2) Vehicle-WIN55,212-2; (3) WIN55,212-2-Vehicle; (4) WIN55,212-2-WIN55,212-2; (5) AM251+vehicle; (6) AM251+WIN55,212-2; (7) AM630+vehicle; (8) AM630+WIN55,212-2; (9) Sham receiving vehicle; and (10) Sham receiving WIN55,212-2. The decreased in mechanical allodynia and thermal hyperalgesia by WIN55,212-2 was significantly greater when it was administered during one week before surgery. In conclusion, pre-emptive use of cannabinoids produced greater antinociceptive effects in a model of neuropathic pain and this effect is mediated by cannabinoid CB(1) and CB(2) receptors.