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. Author manuscript; available in PMC: 2009 Jul 6.
Published in final edited form as: Pharmacol Biochem Behav. 2006 Oct 18;85(2):385–392. doi: 10.1016/j.pbb.2006.09.006

Figure 1.

Figure 1

Percentage of cocaine-lever responding (upper panel) and overall rate of responding (lower panel) in subjects administered either cocaine (n=8, filled circles), amphetamine (n=7, unfilled circles) or morphine (n=7, grey diamonds). All three drugs were administered i.p. immediately before the start of the session. Values adjacent to a data point indicate the number of subjects represented by that point, if less than 8 for cocaine, or 7 for amphetamine and morphine. Percentages of cocaine-lever responding and response rates are expressed as mean ± S.E.M. The shaded area on the bottom panel represents the mean response rate following saline administration ± 20 %.