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. Author manuscript; available in PMC: 2008 Jun 15.
Published in final edited form as: Drug Alcohol Depend. 2007 Jan 19;89(1):52–59. doi: 10.1016/j.drugalcdep.2006.11.020

Figure 2.

Figure 2

Mean (±1 SEM) number of reinforcers earned during initial testing (average of sessions 26–30), the first 9 nicotine challenge tests (sessions 31–39), and the last 6 nicotine challenge tests (sessions 40–45). Rats in the NIC/SAL group (●) received nicotine injections 5-min before and saline injections 1-h after each session depicted in the figure. Rats in the SAL/SAL group (▽) received saline injections 5-min before and 1-h after each session. The SAL/NIC group (□) received saline injections 5-min before and nicotine injections 1-h after each of the first 9 drug test sessions (31–39). For the next six tests (sessions 40–45), the SAL/NIC group was separated into two subgroups, one receiving nicotine injections 5-min before the session (■) and one that continued to receive nicotine injections 1-h after the session (□).