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. Author manuscript; available in PMC: 2014 Dec 1.
Published in final edited form as: J Pain. 2013 Oct 22;14(12):10.1016/j.jpain.2013.08.003. doi: 10.1016/j.jpain.2013.08.003

Figure 3.

Figure 3

Assessment of morphine antinociception and tolerance in CFA-treated rats using the von Frey test. A) Microinjection of morphine produced a significant increase in pressure thresholds that was consistent across the four trials. B) Morphine produced a dose dependent increase in von Frey threshold, but there was no difference in morphine potency on Trial 5 between rats treated with morphine or saline on Trials 1 - 4. The same result was evident in non-inflamed rats except that the range of scores was different because of the lack of allodynia (note the difference in range on the y-axis between Figures A & B vs. C & D). C) Microinjection of morphine caused a significant increase in von Frey threshold that persisted for all four days. D) There was no difference in morphine potency on Trial 5 in non-inflamed rats treated with morphine or saline on Trials 1 – 4.