“…This is consistent with observations that plasticity-restricting PNN components are reduced after heroin self-administration (Van Den Oever et al, 2010) and protein expression of reelin is increased after cocaine self-administration (Host et al, 2010). Interestingly, an increasing number of studies show that experimental manipulations that reduce ECM breakdown or elevate ECM levels interfere with addictive behavior in different animal models of addiction, including behavioral sensitization (morphine, cocaine, and methamphetamine; Maiya et al, 2009;Mizoguchi et al, 2007;Nagai et al, 2004Nagai et al, , 2005b, CPP (morphine, cocaine, amphetamine, methamphetamine, and nicotine; Brown et al, 2007;Maiya et al, 2009;Mizoguchi et al, 2007;Nagai et al, 2004Nagai et al, , 2005bNagai et al, , 2006, cocaine self-administration (Chen et al, 2013), and reinstatement of heroine seeking (Van Den Oever et al, 2010). In contrast, enhancement of synaptic plasticity by ECM breakdown facilitates extinction of the drug memory (Xue et al, 2014), providing a substrate to suppress drug-seeking urges.…”