Effect of estrogen on and sex differences in rotational behavioral induced by repeated treatment with 20 mg/kg cocaine. Left, Mean ± SEM number of net rotations per hour during each of the 12 test sessions. The OVX+E group (n = 8; solid triangles) was treated with 5 μg of EB 30 min before 20 mg/kg cocaine. Open circles represent the data from OVX females (n = 8), open diamonds the data from CAST male rats (n = 8), and solid squares the data from SHAM male rats (n = 7). Right, Mean ± SEM rate of sensitization from linear regression calculated for each rat from the data for the 12 testing sessions. *Net rotations per hour for OVX animals were significantly greater than SHAM (p < 0.0003) and CAST (p < 0.0001) groups; **net rotations per hour for OVX+E animals were significantly greater than OVX (p < 0.0001), CAST (p < 0.0001), and SHAM (p < 0.0001) groups; ***rates of sensitization for OVX+E animals were significantly greater than OVX (p < 0.038), CAST (p < 0.002), and SHAM (p < 0.001) groups.