Figure 6. Blocking kappa opioid receptors in the VTA blocks stress-induced reinstatement of cocaine seeking.

(A) Training protocol: 19 d of intravenous cocaine self-administration (2 h per day) were followed by daily extinction sessions until lever pressing decreased to <15% of responding on the last day of cocaine self-administration. Rats required ≤ 8 days to achieve this criterion. Twenty-four hours following the attainment of extinction criterion, animals were given a microinfusion of nor-BNI or vehicle into the VTA. 24 hours later, they were exposed to a cold swim stressor and tested for reinstatement responding 24 hours later. (B) Total active and inactive lever presses during the reinstatement phase are shown from animals administered vehicle (n = 7) or 2.5 μg (n = 7) nor-BNI into the ventral tegmental area prior to stress. Unlike the vehicle controls, animals that received nor-BNI infusions into the VTA did not show significant reinstatement of cocaine responding as compared to their extinction responding.