Fig. 5.

A The effect of nicotine administered during an extinction trial on non-reinforced responding for cocaine in animals previously treated with saline 3 min prior to cocaine self-administration sessions for 2 weeks. Data are presented as responses per 5 min (mean±SEM). No differences were observed when animals were injected with nicotine (closed circles; injections indicated by the arrow) after 45 min of non-reinforced responding relative to saline (open circles). B Responding on the inactive lever was not significantly different when animals were treated with nicotine relative to when they were treated with saline. Data are presented as the number of responses per 5 min (mean±SEM)