We compared the levels and distribution of the DAMGO-stimulated [35S]GTPγS binding between A/A and G/G mice brains. Representative pseudo-color autoradiograms of DAMGO-stimulated [35S]GTPγS binding in male A/A and G/G mice are shown in Fig. 2. A/A and G/G mice displayed similar regional distribution (Fig. 2). Quantitation of [35S]GTPγS binding in the presence and absence of DAMGO was performed by measuring the density of autoradiograms in brain regions. Net DAMGO-stimulated [35S]GTPγS binding was obtained by subtracting the basal binding from the binding in the presence of DAMGO. Density was converted to radioactivity using calibration curves generated from the [14C] standards. Table 1 shows the combined data of male and female mice of the same genotype and analyses of basal and net DAMGO-stimulated [35S]GTPγS binding. In the VTA, A/A mice displayed significantly lower basal [35S]GTPγS binding, but higher net DAMGO-stimulated [35S]GTPγS binding than G/G mice. In all the other brain regions, there are no significant differences between A/A and G/G mice in basal and net DAMGO-stimulated [35S]GTPγS binding, but G/G mice show a trend of higher basal [35S]GTPγS binding than A/A mice. Moreover, there are large regional variations in basal and net DAMGO-stimulated [35S]GTPγS binding.
