neurons from GIRK1−/− and GIRK2−/− mice support this notion (Koyrakh et al., 2005; Marker et al., 2006). Recent evidence suggests that many GIRK channel subtypes exist in the brain in a cell type- and subcellular compartment-dependent manner (Aguado et al., 2008; Ciruela et al., 2010; Fernández-Alacid et al., 2009; Labouèbe et al., 2007; Perry et al., 2008). For instance, the GIRK3 subunit also seems to add to the repertoire of functional GIRK channels in the brain. In the cerebellum, ultrastructural data have shown that dendritic spines of Purkinje cells and dendrites of granule cells contain GIRK1, GIRK2 and GIRK3 (Ciruela et al., 2010; Fernández-Alacid et al., 2009). However, membrane fractionation analyses have indicated that GIRK2 and GIRK3 are present in distinct membrane microdomains in the hippocampus (Koyrakh et al., 2005), suggesting that the relevance of the GIRK3 subunit in the formation of functional GIRK channels in the hippocampus is different to that in the cerebellum.
