The AI of the opioid mRNAs, opioid peptides, and neurotransmitters in the pgACC. The AI [(R − L)/(R + L)] is a measure of hemispheric differences, which the −1.0 and +1.0 values indicate a complete left or right lateralization, respectively, and the 0.0 value symmetric distribution. Data bars represent the means ± SD. Dashed lines at the −0.33 and +0.33 AI values mark 2-fold differences between hemispheres. Significance in the MANOVA followed by ANCOVAs when appropriate: Lateralization effect, *P < 0.05, **P < 0.01, ***P < 0.001; sex effects, #P < 0.05.