Figure 2.

Repeated AMPH rescues the AMPH-induced striatal BOLD response in STZ-treated rats. A–C, BOLD activation maps were overlaid on high-resolution anatomic templates to depict regional mean postinjection BOLD signal changes (ΔS/S₀, in percent) in response to AMPH challenge (1.78 mg/ml, i.p.) for untreated (euinsulinemic) control rats that received repeated AMPH injections (A), STZ-treated (hypoinsulinemic) rats that received repeated saline injection (B), and STZ-treated rats with a history of repeated AMPH injections (C). D–F, ROI time series within the DAT and IR-rich striatum for all three treatment groups 4 d after the last saline or AMPH injection, i.e., 17 d after STZ. D, Time-series data from the caudate–putamen of each treatment group showing the 15 min post-AMPH response after the 15 min baseline period. E, Comparisons of the area under curve for the pre-AMPH and post-AMPH periods across the three treatment groups in the study reveal significant and equivalent increases in BOLD activation in dorsal striatum after AMPH in both euinsulinemic control and STZ-treated rats with a history of repeated AMPH injection. In contrast, STZ-treated rats receiving AMPH for the first time show a dramatically blunted BOLD signal change. **p < 0.01 versus baseline (one-way ANOVA with Bonferroni's multiple comparison test; n = 8–9 per group). F, Position of right and left ROIs (red voxels) drawn in the anterior and posterior caudate–putamen. Stereotaxic coordinates indicate the approximate rostrocaudal distance from bregma of the multislice images used in this study (Paxinos and Watson, 1998).