Fig. 3.

Repeated stress during abstinence increased reacquisition of nicotine SA begun 24 h after the final stress and induced nicotine taking during the inactive phase of the light cycle. (a) Active lever presses during 5 days of reacquisition under an FR5 schedule were increased by repeated restraint stress compared to non-stress group (Repeated measure ANOVA: p < 0.05). (b) During first 3 days of reacquisition, stress significantly increased nicotine injections both in the dark and light phases (Repeated measure ANOVA: p < 0.05). (c) Cumulative (hourly) nicotine injections in 2 representative rats from non-stress and stress groups on day 1 of reacquisition. Nicotine taking during “lights on” (i.e., inactive phase) was only seen in stressed rats. * p < 0.05 vs. acquisition within group; # p < 0.05 stress vs. non-stress group at same time interval (t-test). n = 5 per group.