Overexpression of MOR in NAc and VTA differentially alters Meth sensitization behavior in mice. a Overexpression of MOR in NAc reduces Meth sensitization. Daily injections of Meth (2.5 mg/kg, days 1 to 5 and 15) progressively increased TOTDIST, HACTV, and MOVETIME, while reduced RESTIME in all animals. Injection of AAV-MOR to NAc significantly decreased Meth-enhanced TOTDIST, HACTV, and MOVETIME, compared to AAV-GFP control (#p<0.05, two-way ANOVA; *p<0.05, post hoc Newman-Keuls test). b Overexpression of MOR in VTA enhanced Meth sensitization. Local administration of AAV-MOR to VTA significantly facilitated the Meth-enhanced TOTDIST and MOVETIME, while RESTIME was significantly reduced (#p<0.05, two-way ANOVA). No significant difference was found in HACTV