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. Author manuscript; available in PMC: 2008 Mar 10.
Published in final edited form as: Behav Pharmacol. 2006 May;17(3):213–222. doi: 10.1097/00008877-200605000-00002

Fig. 1.

Fig. 1

Operant responding in Paired (Paired-CS, Paired-No CS) and control (Nal-Naive, Unpaired) groups from Experiment 1 as a function of operant interval (Pre-CS, CS 1–10, CS 11–20). A) On Conditioning Days, responding during Pre-CS session (left panel) were suppressed in both the Paired groups as conditioning proceeded (*p < 0.05 vs. Unpaired and Nal-Naive controls), but the effect in the Paired-No CS group was significantly greater than in the Paired-CS group (†p < 0.05, Paired CS vs. Paired-No CS). In the CS 1–10 interval (center panel), responding was predictably suppressed totally within 2 sessions in the Paired groups. A transient decrease in operant responding due to CS novelty followed by habituation was noted in both control groups during the CS 1–10 interval ($p < 0.05, main effect of Conditioning Day). In the CS 11–20 interval (right panel), responding again was predictably suppressed in the Paired groups experiencing naloxone-precipitated withdrawal during operant testing on Conditioning Days. Somewhat unexpected was a modest suppression in responding that emerged over Conditioning Days in both the Nal-Naive and Unpaired control groups ($p< 0.05, main effect of Conditioning Day); this may reflect the emergence of a mild spontaneous withdrawal from repeated daily morphine treatments (see text for further details). B) On Test Day, responding in the Pre-CS session (left panel) was again suppressed in both Paired groups (*p < 0.05 vs. Unpaired and Nal-Naive controls), with the Paired-No CS groups showing greater suppression in this interval than the Paired-CS group (†p < 0.05). Operant responding during the first 10 minutes of CS session (center panel) were suppressed in the Paired-CS group relative to the both control groups(*p < 0.05) and relative to Paired-CS responding in the Pre-CS interval ($p < 0.05 vs. Pre-CS), but responding in the Paired-No CS group actually increased significantly from the Pre-CS to the CS 1-10 interval ($p<0.05 vs. Pre-CS). There was no difference in responding during final 10 minutes of CS session (right panel) between any treatment groups.