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. 2013 Jul 17;38(12):2508–2514. doi: 10.1038/npp.2013.155

Figure 4.

Figure 4

Effect of intra-NAc infusion of δ or μ antagonist cue-induced cocaine-seeking behavior after 1 day or 30 days of forced abstinence. (a) Day 1: Number of active lever presses after infusion of naltrindole (δ antagonist) is significantly higher than after infusion of CTAP (μ antagonist; 3 μg) and showed the same effect as anti-β-endorphin antibody infusion (anti β-endorphin). *p<0.05 vs aCSF-infused rats. (b) Day 30: Antagonism of the δ receptor reversed the effect of exogenous β-endorphin on cue-induced cocaine-seeking behavior. The number of active lever presses after infusion of naltrindole together with β-endorphin is significantly higher than after infusion of CTAP (3 μg) with β-endorphin or infusion of a β-endorphin alone. *p<0.01 vs aCSF-infused rats. Values are expressed as mean±SEM; n=9 rats per group.