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. Author manuscript; available in PMC: 2019 May 1.
Published in final edited form as: Pain. 2018 May;159(5):919–928. doi: 10.1097/j.pain.0000000000001167

Figure 1. Morphine infusion for 7 days causes hypersensitivity that resolves by day 21.

Figure 1

Morphine or saline was delivered by subcutaneously implanted osmotic minipump for seven days. Morphine-primed rats showed periorbital (A) and hindpaw (B) allodynia to von Frey filaments beginning on day 4 of morphine treatment. Allodynia resolved by day 18 (A and B). Morphine-treated rats also showed hindpaw hyperalgesia on the Randall-Selitto test on day 7 of drug treatment compared to morphine-treated baseline measures and compared to saline rats on day 7 (C). **** p<0.0001, *** p<0.001, ** p<0.01, * p<0.05 significant difference compared to baseline or as indicated. Allodynia experiments (A and B) n=7 per group, Randall-Selitto experiment (C) n= 98 saline, 64 morphine (data combined from rats used in all experiments in this paper). Data analyzed by two-way ANOVA followed by Tukey’s test for multiple comparisons.