Loss of mesolimbic-specific opioid- and cocaine-induced place preference in chronic pain. a, Repeated conditioning to intra-VTA DAMGO (1 ng) failed to produce a robust place preference in the PNI groups, whereas a high dose of DAMGO (25 ng) produced a robust place preference in both the sham and PNI groups. Pretreatment with the microglial inhibitor minocycline (30 mg/kg) recovered intra-VTA DAMGO (1 ng) place preference in the PNI group. Top left pictograph depicts intra-VTA injection sites. *p < 0.05, **p < 0.01, ***p < 0.001. Error bars indicate SEM. b, Cocaine (100 μg) administered directly into the NAc produced a place preference in the sham group, but not the PNI group. Left pictograph depicts intra-NAc injection sites. *p < 0.05. Error bars indicate SEM.