Figure 3.

Comparisons of the long-term effects of chronic and binge methamphetamine regimens on reward thresholds (A), latency to respond (B), extra responses (C) and timeout responses (D) in response to acute methamphetamine challenge. Acute methamphetamine challenge induced reward enhancement as indicated by significantly lower reward thresholds at all doses with no significant effects of methamphetamine regimen (A). Both 0.4 and 0.8 mg/kg methamphetamine led to significantly decreased latencies after both regimens compared with saline (B). The binge regimen led to significantly elevated extra responses overall and, specifically, after 0.4 mg/kg methamphetamine compared with saline (C). A similar trend was observed for the chronic regimen when compared with saline. Acute methamphetamine challenge reduced timeout responses at the highest dose (0.8 mg/kg) with no significant effects of methamphetamine regimen (D). Data are expressed as mean ± SEM.

* p<0.05, *** p<0.001 significantly different from 0 mg/kg methamphetamine (A,D).

^ap<0.05 between saline and both the binge and chronic regimens (B).

^bp<0.05 between saline and the binge regimen; p<0.1 between saline and the chronic regimen (C).

^{# #}p<0.05 significant main effect of methamphetamine regimen with the binge regimen significantly different to saline (B,C).