Fig. 3.

Self-administration of an initial infusion of cocaine late in the session (at the time the second infusion would normally occur) does not result in a diminished response, indicating that the reduced response to the second infusion shown in Figures 1 and2 is not an artifact of the time into the session. Solidcircles represent an early first infusion;opencircles represent a late first infusion. The number of trials is as follows: M103,n = 4 early infusions and 6 late infusions; M32,n = 6 early infusions and 5 late infusions; M49,n = 14 early infusions and 11 late infusions; M47,n = 10 early infusions and 11 late infusions.