We next examined and quantified key cellular and molecular markers of excitatory neurotransmission in the NAcc of wild-type and Girk−/− mice. First, we quantified excitatory synapse density in medium spiny neurons of the NAcc using an optical dissector approach (Sterio 1984). Synapse density in the NAcc from Girk1−/− (1.31 synapses/μm3) and Girk2−/− (1.35 synapses/μm3) mice was ~15% higher as compared to wild-type control (1.12 synapses/μm3) (Fig. 7A-D). Moreover, synaptic densities of GluR1 (Fig. 7E-H) & GluR2/3 (Fig. 7I-L) were significantly elevated (~2-fold) in medium spiny neurons in the NAcc from Girk1−/− and Girk2−/− mice. Similar increases in synapse density and AMPA subunit labeling were observed in both the NAcc shell and core.
