Lastly, the propensity of Lwt/+ mice to express a conditioned place preference (CPP) to ethanol (1.75g/kg, i.p.) was assessed. Wild-type animals showed a robust place preference (P<0.001, Wilcoxon signed rank test), while Lwt/+ mice develop a significant place preference (P = 0.032, Wilcoxon signed rank test) (Figure 9). There is not a significant difference between the two genotypes in time spent on the ethanol-conditioned side (P = 0.0818, Mann-Whitney test) (Figure 9), although there is a trend towards greater ethanol CPP in wild type animals. We tested 11 animals per genotype; it is possible that by testing larger numbers of animals, we would detect a significant difference between Lwt/+ and +/+ animals.
