Figure 1. Expression of melatonin MT₂ receptors in rat retinal ganglion cells (RGCs).

Double immunofluorescence labelling was performed using the antibody against MT₁ or MT₂ receptors on acutely dissociated RGCs labelled retrogradely by injecting fluorogold (FG) into the superior colliculus bilaterally. A, Western blot of whole rat retinal extract using the antibody against MT₁, revealing a single band at the corresponding molecular weight of around 45 kDa. Ba–Bd, a RGC, double labelled by FG and MT₁. Ba is the DIC image of the cell. The cell was labelled by FG (Bb), but not by MT₁ (Bc). Bd is the merged image of Bb and Bc. C, Western blot of whole rat retinal extract using the antibody against MT₂, also revealing a single band at around 45 kDa, corresponding to the molecular weight of the native MT₂ receptor. Da–d, another RGC labelled by FG and MT₂. Da is the DIC image of the cell. Dd is the merged image of Db, showing labelling for FG, and Dc, showing labelling for MT₂. Note that the labelling for MT₂ is primarily located on the membrane of the soma, and some punctate labelling is also observed in the dendrites. Ea, a RGC labelled by FG. Eb, no immunoflorescence labelling for MT₂ receptors could be found when the MT₂ antibody was pre-absorbed with the immunizing antigen. Scale bars, 10 μm.