Fig. 1

Analysis of mRNA levels and phenotypic evaluation of transgenic mice. a PCR analysis of a litter from a single mating showing wild-type (WT) (+ / +), heterozygous (HT) (+ / −), and homozygous (−/−) σ2R mice. b Deletion of σ2R did not significantly alter the expression of σ1R, HINT1 or MOR. c Body weight gain in grams, horizontal activity, rearing time in seconds, and latency to fall from the rotarod in seconds for the three groups of mice. d Learning performance in the passive avoidance test. Six to eight mice (5 weeks of age) were subjected to each treatment, and the data represent the means ± SEMs. * Indicates significantly different from the WT mice, degrees of freedom (df) = 16, all data were analyzed by pairwise Holm-Sidak multiple comparison tests following ANOVA, p < 0.05. σ1R, HINT1 and MOR represents sigma type 1 receptor, histidine triad nucleotide-binding protein 1, and mu-opioid receptor, respectively