Fig. 1. Effects of ketamine on mechanical hyperalgesia (  A ), tactile allodynia (  B ), and weight-bearing changes (  C ) induced by left hind paw plantar incision. A hind paw plantar incision was realized on rats during halothane anesthesia on D⁰. Three injections of ketamine (3 × 10 mg/kg, administered subcutaneously; n = 12) or saline (n = 12) were performed. The first one was performed 30 min before the surgery, and the following injections were performed every 5 h. The three pain parameters were evaluated before surgery on D⁻², D⁻¹, and D⁰; 2, 4, 6, and 10 h after surgery on D⁰; and subsequently once daily for 8 days. At the end of the experiment (D⁸), all rats were injected with naloxone (1 mg/kg subcutaneous), and the three pain parameters were measured 5 min later. (  Inset ) Algesic index showing the variations of mechanical hyperalgesia, tactile allodynia, and weight bearing on the days after the incision. Pain parameters values and algesic index are expressed as mean ± SD. # Dunnett test,  P < 0.05 compared with the D⁰basal value.  Open circle = saline-treated rats;  open diamond = ketamine-treated rats.