Fig. 12. The effects of an intrathecal injection of different doses of SB-269970 (1, 3, and 10 μg) and SB-258719 (5, 10, and 20 μg) on the fixed maximal dose of systemic tramadol-induced (30 mg/kg) (  A and  B ) and O-desmethyltramadol (M1)-induced (10 mg/kg) (  C and  D ) thermal antihyperalgesia. SB-269970 and SB-258719 were intrathecally given 30 min after subcutaneous administration of tramadol (80 mg/kg) and M1(10 mg/kg). N = 8 per group. * Differences corresponding to the dose of tramadol and M1 alone  P < 0.05 (Bonferroni  post hoc test).