Fig. 2

The effect of route of administration on the time course and magnitude of antagonist effect on equiactive cocaine or apomorphine concentrations depicted as agonist concentration ratio − 1. Each point represents cocaine or apomorphine concentration ratio − 1 at the time of each self-administration after the injection of antagonist. The concentration ratios were calculated by dividing the agonist concentration at the time of each self-administration after the antagonist injection by the mean baseline agonist concentration in each session. The curve through each data set represents the best fit generated by a pharmacokinetic model using WinNonlin. The vertical line represents the time of maximum effect.