Fig. 1.

Estrus females form associations between cocaine and predictive cues that enhance motivation later. a Timeline of experiments. Animals were first given non-contingent cocaine (0.3 mg/kg/inj) on a VT300s schedule paired with a cue light (n = 4–9 per group). Next animals acquired self-administration in the absence of cues. Finally, the threshold procedure was used to assess consummatory and appetitive responding in the presence or absence of cues. b Estrus-paired cues increased motivation to obtain cocaine as compared to diestrus-paired or male rats. **p < 0.01 compared to no cue. c Animals were more motivated to self-administer cocaine in the presence of estrus-paired cues. There was no effect of cues in diestrus-paired or male animals, showing that the cue value, not just the presence of a cue light, is the critical determinant of changes in motivational drive. **p < 0.01 compared to male and diestrus females. d Cocaine intake did not differ between groups with cue or without. e Representative demand curves showing cocaine consumption as a function of price in males and females with or without cues—data is based off of the cycle state in which the cues were paired. All data are presented as mean ± S.E.M