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. 2010 Sep;334(3):1042–1050. doi: 10.1124/jpet.110.169243

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Copyright © 2010 by The American Society for Pharmacology and Experimental Therapeutics

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Fig. 7. — Tolerance to morphine in the warm-water tail immersion test. Mice were implanted with either a PP or 75-mg MP 72 h before they were challenged with morphine. Mice were then injected with various doses of morphine subcutaneously, and their tail immersion latencies were determined for construction of dose–response curves 30 min later. Data are expressed as mean %MPE ± S.E.M. Each data point represents 6 to 10 mice. The morphine ED₅₀ values were as follows: wild-type PP (), 7.5 mg/kg (95% CL 6.4–8.9); wild-type MP (), 86.8 mg/kg (95% CL 47.9–157.4); CD38 KO PP (▴), 54.9 mg/kg (95% CL 40.8–73.8); CD38 KO MP (♦), 167.7 mg/kg (95% CL 109.3–257.3). Both the wild-type mice and CD38 KO mice developed tolerance to morphine; however, morphine was less potent in the placebo-treated mice compared with the wild type and less potent in the tolerant mice compared with wild type. Wild-type mice developed approximately 12-fold tolerance in this model, whereas the CD38 KO mice developed only a 3-fold tolerance.

Inline graphic — Tolerance to morphine in the warm-water tail immersion test. Mice were implanted with either a PP or 75-mg MP 72 h before they were challenged with morphine. Mice were then injected with various doses of morphine subcutaneously, and their tail immersion latencies were determined for construction of dose–response curves 30 min later. Data are expressed as mean %MPE ± S.E.M. Each data point represents 6 to 10 mice. The morphine ED₅₀ values were as follows: wild-type PP (), 7.5 mg/kg (95% CL 6.4–8.9); wild-type MP (), 86.8 mg/kg (95% CL 47.9–157.4); CD38 KO PP (▴), 54.9 mg/kg (95% CL 40.8–73.8); CD38 KO MP (♦), 167.7 mg/kg (95% CL 109.3–257.3). Both the wild-type mice and CD38 KO mice developed tolerance to morphine; however, morphine was less potent in the placebo-treated mice compared with the wild type and less potent in the tolerant mice compared with wild type. Wild-type mice developed approximately 12-fold tolerance in this model, whereas the CD38 KO mice developed only a 3-fold tolerance.