To further examine the effect of A112G on MOPR expression, we carried out [3H]DAMGO (3 nM) binding to the MOPR in membranes of four grossly dissected brain regions [thalamus, cortex, hippocampus, and CPu (including NAc; CPu+ NAc)] in A/A and G/G mice. Other brain regions did not yield sufficient amounts of tissues for [3H]DAMGO binding in an individual animal. Compared with A/A mice, G/G mice had decreased specific [3H]DAMGO binding in the thalamus and cortex (Table 2). Further analysis showed that female A/A mice exhibited higher specific [3H]DAMGO binding in thalamus than female G/G mice. In cortex, both male and female A/A mice showed higher binding than G/G mice (Fig. 3). In contrast, no genotype differences were observed in the hippocampus and CPu+NAc (Table 2, Fig. 3).
