The percentage of animals that met criteria for acquisition of cocaine self-administration each day. OVX rats treated with estradiol or vehicle were tested 5 days a week for 5 weeks with increasing doses of cocaine each week.
Open circles - OVX; closed triangles - 1 µg E; closed circles - 2 µg E; open diamonds - 5 µg E; closed squares - E-pellet.
*There was a significant effect of 2 µg treatment on the percentage of rats that acquired self-administration during week 2 relative to the OVX and OVX+pellet groups (p<0.01).