Fig. 9.

Effect of repeated amphetamine pretreatment on DCC receptor expression in the ventral tegmental area of adult dcc heterozygous (+/−) and wild-type (+/+) mice. Results from Western blot analysis of mean DCC immunoreactivity (and standard error of the mean) in the ventral tegmental area (VTA) of adult male dcc +/− and +/+ mice that received a pretreatment with saline or with d-amphetamine sulfate (AMPH; 4 mg/kg of amphetamine, 5 injections, once every other day). These mice were tested for sensitization 1 week after the last day of the pretreatment phase by injecting them with 2 mg/kg of amphetamine intraperitoneally (see Fig. 8); their brains were processed for Western blot immediately after this test (n = 7 per group). Repeated administration of amphetamine induced significant increases in DCC receptor expression in the VTA of +/+ mice, but did not alter DCC expression in dcc +/− mice. As expected, dcc +/− exhibited significantly less (about half) DCC expression than saline-pretreated wild-type controls (significant genotype × drug pretreatment interaction: F _1,15 = 4.79, p = 0.044; post hoc Student t tests: significant difference between amphetamine- and saline-pretreated +/+ groups, p < 0.05, and significant difference between saline-pretreated dcc +/− and saline-pretreated +/+ mice, p < 0.001). Reproduced with permission from Yetnikoff et al.⁸⁶