Fig. 1.
Cocaine induced CPP was blunted in mice lacking β-endorphin (betaend-) compared to their wild-type littermates (betaend+). The data represent mean (±S.E.M.) of the amount of time that mice (n = 8 mice per genotype) spent in the drug-paired chamber on pre- and postconditioning test day. ***P<0.001 compared to its respective preconditioning test day.