FIG. 1

Left: Actual response record of a rat maintained on a fixed-ratio 15 schedule of cocaine self-administration at a unit dose of 0.75 mg/kg. The columns represent the total number of responses in sequential 5-min periods when the lever is active (RESP) and during the time-out periods (TO RESP) when the lever is inactive. The total number of injections received is indicated in (REW). The bottom record shows the response record over time and each mark represents the delivery of a cocaine injection. From Caine et al. (6) with permission. Right: Typical patterns of cocaine substance abuse in the rat as a function of unit dose, and following pretreatment with a dopamine-receptor antagonist. The abscissa represents time in minutes, and each mark denotes delivery of a cocaine injection. From Caine et al. (6) with permission.

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published 2000