Table 1.

Effect of the unit dose of cocaine on the inter-injection intervals and cocaine level at the time of injection as well as the cocaine level at the time of the first lever press during when access to cocaine was terminated in FR1 cocaine self-administration sessions. Values represent the mean and standard error of the mean (from 7 rats) These data are from sessions conducted as shown in the representative FR1 self-administration session in Fig. 1.

	Inter-Injection Interval (minutes)	Calculated Cocaine Level (μmol/kg)
Injections (0.3 μmol/kg cocaine unit dose)	0.89 ± 0.06	4.04 ± 0.27
Injections (3 μmol/kg cocaine unit dose)	7.4 ± 0.36	3.75 ± 0.23
First lever press at Unloading (when access to cocaine was terminated)	N/A	3.83 ± 0.21