Knockdown of the Arc/Arg3.1 protein in the amygdala abolished conditioned place aversion formation induced by morphine withdrawal. A, Representative Western blot image of in vitro knockdown of Arc/Arg3.1 protein expression in primary cortex neurons by Arc/Arg3.1 shRNA. B, Representative image of in vivo lentivirus-infected regions in the amygdala visualized by fluorescence microscope. C, Quantified data of in vitro knockdown of Arc/Arg3.1 protein expression (left) and in vivo knockdown of Arc/Arg3.1 disruption of conditioned place aversion formation (right) by Arc/Arg3.1 shRNA. Error bars represent mean ± SEM. ***p < 0.001, compared with control shRNA- infected groups, two-tailed Student's t test.