Induction of sensitization. (A) The administration of 50 μl of carrageenan in the knee joint induced an evident inflammation. The circumference of the knee increased significantly 16 h after the injection of carrageenan. Neuropathy was induced seven days before the experiment following the partial sciatic nerve ligation technique. (B) Mechanical hyperalgesia was studied by applying a series of von Frey filaments previous to and at days 1, 4 (not shown) and 7 after the nerve ligation. (C) Thermal hyperalgesia was assessed by measuring paw withdrawal latencies to 55°C radiant heat using a similar timing. An intense mechanical and thermal hyperalgesia was observed in all tests made after the induction of neuropathy (**P < 0.01, ***P < 0.001, comparison vs. control response with the two tail unpaired t-test).