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. 2012 Mar 16;7(3):e33435. doi: 10.1371/journal.pone.0033435

Figure 2. Effects of chronic methionine treatment on the establishment of cocaine-, morphine- and food-CPP.

Figure 2

Mice were injected subcutaneously with 1 g/kg (6.6 mmol/kg) L-methionine twice a day for 25 consecutive days before (15 d) and during CPP procedures (10 d) respectively. (a) Methionine significantly inhibited the establishment of cocaine-CPP at 20 mg/kg cocaine; (b) Methionine abolished the establishment of cocaine-CPP at 5 mg/kg cocaine; (c) Methionine did not affect the establishment of morphine-CPP; (d) methionine did not affect the establishment of food-CPP. *p<0.05 and ** p<0.001, pretreatment in comparison with posttreatment; **p<0.001, postconditioning in comparison with preconditioning within the same groups. Data are expressed as mean ± SEM. [S-S: n = 8; M-S: n = 7; S-C: n = 10(20 mg/kg); n = 7(5 mg/kg); M-C: n = 10(20 mg/kg) n = 6(5 mg/kg); S-M: n = 10; M-M: n = 8; S-F: n = 10; M-F: n = 8].