Figure 1. Effect of intrathecal morphine administered before (preincision) or after (postincision) foot incision on punctate mechanical hyperalgesia from 1 h to 6 days later. The results are expressed as raw withdrawal threshold versus time data. Each line represents one rat. The withdrawal thresholds are on a log scale. (A) Diagram of the plantar aspect of the rat foot showing site of application of von Frey filament (small circle) and site of application of plastic disc (larger, darkened circle). (B) Withdrawal thresholds after incision in saline-treated rats. (C) Withdrawal thresholds of rats administered 5 micro gram of intrathecal morphine 15 min before incision. (D) Withdrawal thresholds of rats administered 5 micro gram of intrathecal morphine after incision. Pre = time before foot incision. MS = morphine sulfate. *P < 0.05 versus pre by Friedman and Dunnett's test. (dagger)P < 0.05 versus saline by Kruskal-Wallis and Dunn's test.