Figure 2.
Acquisition of cocaine self-administration under short (ShA, 1-h session) and long (LgA, 6-h session) access conditions. The graph shows the number of infusions (mean±SEM) earned by the ShA and LgA groups during the initial 10 days of acquisition of cocaine self-administration and the subsequent 20 days when LgA rats had access to cocaine for 6 h per day, whereas ShA rats continued to have access for 1 h per day. The number of cocaine infusions earned are shown for the 1-h session for ShA rats for the 30 days of testing and for the entire 6-h session for LgA rats from day 20 onward, as well as for the first hour of the 6-h session for LgA rats. ***p<0.001, significant escalation of cocaine self-administration compared with day 10 in LgA rats.