Figure 6.

Effect of tumor injection on conditioned place preference (CPP) to morphine. Mice were injected with tumor into the tongue, habituated on day 5, conditioned with either a vehicle- or morphine-paired chamber for one hour on days 6–8 and tested for CPP on day 9. The CPP score is the ratio of time spent in drug- or vehicle-paired chamber/total time spent in both-chambers. (a) Mice injected with HSC2 spent significantly more time in the morphine 3 mg/kg i.p. paired chamber than the vehicle chamber. (b) Mice injected with non-pain producing colon cancer; HT29 cells spent no significant difference in amount of time spent in the morphine-paired chamber as the normal control mice. Data represented as mean ± SEM and analyzed by two-way ANOVA with p < 0.05 as significant. n = 12/group.