However, the larger spatial resolution of the histoblot technique compared with immunoblot allowed us to detect marked differences in the level of immunoreactivity and expression profiles in a layer-specific manner in the cerebellum. Thus, the expression of GIRK2 decreased progressively with age, whereas the expression of GIRK1 and GIRK3 increased progressively during postnatal development to reach adult levels. The exception was the expression of GIRK1 in the molecular layer, which increased by P10 and then decreased following a similar pattern as GIRK2. Given that GIRK1 and GIRK2 are mainly expressed in cerebellar granule cells (Aguado et al., 2008; Ciruela et al., 2010), their similar expression pattern in the molecular layer during the first and second postnatal week indicates that they are co-expressed in granule cells migrating from the external to the internal granular layer, in agreement with previous immunohistochemical studies in the cerebellum (Slesinger et al., 1996). Although GIRK3 is also expressed in granule cells (Aguado et al., 2008; Ciruela et al., 2010), its differential expression pattern in the molecular layer probably indicates its steady-state expression profile in Purkinje cells, the cell type showing the highest expression level for this subunit (Aguado et al., 2008).
