Fig. 2. (a) Colocalization of GABA_B receptors and clathrin. In cells labeled with a polyclonal antibody against GABA_B receptor (red) and a monoclonal antibody against clathrin HC (green), a clustered distribution of fluorescence is detected on the plasma membrane and inside the cytoplasm. GABA_B receptors and clathrin vesicles are partly colocalized (yellow fluorescence). Bar, 10 µm. (b) 2D cytofluorogram. Colocalized pixels are visualized in blue. (c) Ultrastructural localization of GABA_B receptors in Paramecium cells using 10 nm gold particles in electron microscopy. GABA_B receptor immuno-analogue is present in coated pits. Bar, 100 nm. (d) Immunogold labeling in the transmission electron microscopy confirms the colocalization of GABA_B receptors (15 nm gold particles) and clathrin (10 nm gold particles) in coated pits. Bar, 100 nm.