Mice with oprm1 A112G, the equivalent of the OPRM1 A118G, exhibited lower MOPR expression in some, but not all, brain regions. The brain region-specific N-glycosylation may contribute to differential effects of A112G on MOPR expression. The observed reduction in MOPR expression in brain regions by the A112G is likely to be involved in attenuated morphine-induced antinociception, hyperactivity, and locomotor sensitization. Our findings provide some insights into the observed genotype differences in behavioral responses between A/A and G/G mice, which may be extended to the differences between genotypes in humans.
