Figure 1.

Design, MA consumption, and fluid consumption data for experiment 1. With increasing MA concentration, the selectively bred MAHDR mice increase their MA consumption to binge-like levels and sustain that level of consumption for another 12 days. a: Experimental design. The MA group had 18h daily access to 1 water tube and 3 MA tubes, all of which contained the same concentration of MA in water. MA concentration was increased as shown in the diagram and then there was a protracted period of 80 mg/l MA access. The controls had daily access to 4 water tubes, during the same 18h period (control group details not shown). During the remaining 6h of each day, both groups had access to 1 water tube (not shown). After the 28-day MA drinking period, the MA group was divided into two groups and one was tested for immobility using the tail-suspension test (TST) and then the forced swim test (FST) 6h after MA access was withdrawn (Group 2); the other was tested 30h after withdrawal of MA access (Group 3). Control group mice (Group 1) were also divided in half and tested at these times. b: mean (± SEM) mg/kg/18h MA consumed for MA concentrations offered for 4 days each; c: mean (± SEM) mg/kg/18h MA consumed when access to 80 mg/l MA was extended for an additional 12 days. d and e: mean (± SEM) total fluid consumed during the periods in B and C. n = 14–16/group/sex. **p<.01, ***p<.001, compared to the next lower MA concentration for Group 2 and 3 data in b and d; +p<.05, ++p<.01, +++p<.001 for the comparison of each MA group (Groups 2 and 3) to the control (Group 1) at the indicated MA concentration (d) or for the main effect of group (e).