Fig. 1.

The effects of saline or cocaine on locomotor activity in an open-field arena. Injections were given 90 min after rats were put into the arena for the first time. A Time course showing activity in 5-min bins for 90 min before and 30 min after injection with saline (n = 10) or 10 mg/kg cocaine (n = 14). B Cumulative activity is shown for the 30-min following saline or cocaine injection. Rats given cocaine were characterized as LCRs or HCRs (n = 7/group) if their response fell below or above, respectively, the median value for the population (see “Materials and Methods” for details of characterization). *** p < 0.001, compared to LCRs and to saline-treated rats