Figure 2

Participation of the cannabinoid system in motor cortex stimulation (MCS)-induced analgesia. (A) Nociceptive threshold evaluated in the right hind paw of rats with peripheral neuropathy pre-treated with saline (CCI + saline), chronic constriction injury (CCI) rats pre-treated with saline and submitted to MCS (CCI + Saline + MCS), and CCI rats pre-treated with cannabinoid receptor antagonist AM251 and submitted to MCS (CCI + AM251 + MCS). CCI was performed in the right paw and cortical electrodes were implanted in the left hemisphere. The nociceptive test was performed before CCI (IM, initial measurement), and 14 days after CCI (FM, final measurement). One hour after injection of saline (400 μL) or AM251 (1 mg/kg; intraperitoneally), animals were submitted or not to MCS and re-evaluated on the nociceptive test (FM + MCS). Naive rats pre-treated only with AM251 were also evaluated. Values represent the mean ± SEM (n = 5 per group). *P < 0.05 compared with IM. Photomicrographs illustrating glial fibrillary acidic protein (GFAP) immunofluorescence in the dorsal horn of the spinal cord (DHSC) of CCI (B), CCI + Saline + MCS (C), and CCI + AM251 + MCS (D) animals.