Figure 2.

The effects of a timeout period on BDD self-administration behavior. Data from a representative animal during a 6 h BDD schedule consisting of alternating 5 min access periods to the BDD lever and 25 min timeout periods. (a) The event record. Bars indicates a response on the lever, and the height of the bar (scale equals a 1.0 mg/kg infusion) represents the size of the injected dose. The top line shows responses during the full 6 h session. The middle line illustrates the event record of a single 5 min BDD access period. The bottom line is an expansion of a 20-s period in which the animal self-administered a cluster of responses consisting of a mixture of relatively long and short HD responses. (b) The cumulative pump duration throughout the session. The gray shading indicates the 5 min access period. (c) The modeled brain-cocaine concentration throughout the session.