DAMGO-stimulated [35S]GTPγS binding, a measure of MOPR-mediated G protein activation (Traynor and Nahorski, 1995; Sim, Selley, and Childers, 1995), was performed on coronal sections of both the A/A and G/G mouse brains at 3 anatomical levels. There is no difference between A/A and G/G on the overall anatomical distribution of G protein activation; therefore, representative autoradiograms of DAMGO-stimulated [35S]GTPγS binding in male A/A mice are shown in Fig. 1. High levels of DAMGO-stimulated [35S]GTPγS binding were observed in the cortices, CPu, NAc in the telencephalon (Fig. 1A) and in the thalamus, hypothalamus and amygdala in the diencephalon (Fig. 1B). In the midbrain, DAMGO-stimulated [35S]GTPγS binding were found in the substantial nigra, PAG and VTA, albeit at lower levels (Fig. 1C).
