Figure 1.

Heroin intake during a test session as measured by change in number of infusions from previous training day (Figure 1A, left) and total number of infusions during the test session (Figure 1B, right). Horizontal axes depict testing condition: vehicle + vehicle (VEH), estradiol + progesterone (E+P), estradiol + vehicle (EST), and vehicle + progesterone (PRO). Vertical lines indicated 95% confidence limits (left) and SEM (right). Asterisks indicate significant difference from previous day (left) and vehicle control (right).