Ultrastructural analyses were performed with a Jeol 1010 electron microscope (Peabody, MA). Electron photomicrographs were captured with a CCD camera (MegaView III Soft Imaging System; Munster, Germany). Digitized electron images were modified for brightness and contrast with Adobe Photoshop version 7.0. Quantification of GluR1 and GluR2/3 immunolabeling was performed in ultrathin sections obtained from 3 separate panels of wild-type, Girk1−/−, and Girk2−/− mice. Areas in the VTA and Nacc were chosen at random and images were captured at a magnification of 50,000X. In the VTA, only those synapses consisting of an axon terminal apposed to a PSD located on a dendritic shaft labelled for TH were included in the analysis. In the Nacc, only those synapses consisting of an axon terminal apposed to a PSD present on a dendritic spine were included in the analysis. In both locations, the length of the PSD was measured and the number of immunoparticles per PSD was tabulated. There was no impact of Girk ablation on PSD length (not shown).
