Compartmentalisation of voltage-gated potassium (Kv) channel subunits Kv4.2 and Kv4.3 in cerebellar cells. (A,B) Bar graphs showing the percentage of immunoparticles for Kv4.2 and Kv4.3 in neuronal compartment in the molecular layer. Immunoparticles for Kv4.2 were mostly localised at the postsynaptic compartment (99% of all particles), while Kv4.3 was distributed at postsynaptic (88.4%) and presynaptic (11.6%) compartments. (C,D) Bar graphs showing the percentage of immunoparticles for Kv4.2 and Kv4.3 in the neuronal compartment in the granule cell layer. A total of 667 immunoparticles for Kv4.2 and 771 for Kv4.3 were analysed. Postsynaptically, immunoparticles were detected in dendrites of GCs (91.6% for Kv4.2; 82.2% for Kv4.3), distributed along the plasma membrane (46.3% for Kv4.2; 62.3% for Kv4.3) and at cytoplasmic sites (53.7% for Kv4.2; 37.7% for Kv4.3). Presynaptically, immunoparticles were detected in mossy fibre terminals (8.4% for Kv4.2; 17.8% for Kv4.3), distributed at cytoplasmic sites (87.5% for Kv4.2; 53.3% for Kv4.3) and along the plasma membrane (12.5% for Kv4.2; 46.7% for Kv4.3). (E,F) Histogram showing the distribution of immunoparticles for Kv4.2 and Kv4.3 in relation to glutamate release sites in dendritic spines of PCs. About 46% of immunolabelled Kv4.2 and 52% of immunolabelled Kv4.3 were located in a 60–300 nm wide band. These data show that Kv4.2 immunoparticles were more equally distributed along PC spines, while immunoparticles Kv4.3 were skewed toward the PSD of PC spines.