By using the GTPγ[35S] autoradiographic analysis, we aimed to assess the brain regional μ-opioid receptor signal transduction at the G-protein level in GluA1−/− and GluA1+/+ mice. Representative autoradiographs are depicted in Figure 6. Basal and non-specific bindings were equal in both genotypes and sexes across all brain regions (data not shown). In DAMGO-stimulated regional EC50-values (Table 1), no statistically significant differences were detected between genotypes or sexes (p's>0.05). However, the EC50 value was higher in the VTA than in the amygdala, caudate-putamen, hypothalamus, locus coeruleus, nucleus accumbens and thalamus (ANOVA for region F9,86 = 3.71, p<0.01, followed by Bonferroni test) suggesting lower potency for DAMGO in the VTA. In maximal stimulation (Table 1), no differences were observed between genotypes or sexes in any of the brain regions studied (p's>0.05). GTPγ[35S] binding stimulated by 10 µM morphine was similar between GluA1−/− and GluA1+/+ mice in all brain regions studied (data not shown).
