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H. Oi, A.T. Ishida; Dopamine Receptor–like Immunoreactivity in DiI–Filled Rat Retinal Ganglion Cells . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3112.
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To morphologically characterize adult rat retinal ganglion cells (RGCs) displaying D1a–type dopamine receptor–like immunoreactivity.
Kao and Sterling (2003 J Neurocytol) showed that the lipophilic dye "DiI" could be applied to immunostained retinal neurons to reveal their anatomical properties. Using an antiserum directed against D1a–type dopamine receptor (Chemicon), we immunostained whole retinas of adult (P60–120) Long–Evans rats after retrogradely filling small numbers of ganglion cells by depositing DiI in the optic nerve (under sodium pentobarbital anesthesia). Somata in the inner nuclear and ganglion cell layers were Nissl stained to determine the thickness and borders of the inner plexiform layer. Cells were imaged by laser scanning confocal microscopy.
RGCs were readily identified by presence of DiI in a singularly long process that extended from each soma into the optic fiber layer. After DiI was allowed to diffuse into the somata and dendrites of these cells for as long as 1 week, co–localization of DiI and D1a–receptor immunostaining was found in cells displaying different morphologies. At distances between 1 and 3 mm from the optic nerve head, some cells presented a combination of large somata (12–20 µm dia) and large dendritic fields (450–500 µm dia). These resembled rat RGCs classified in previous studies as "α" and "RGA2". Other cells presented both smaller somata (≤12 µm dia) and smaller dendritic fields (≤200 µm dia).
Our results indicate that morphologically different types of RGC possess D1a–type dopamine receptors in adult rat retina. One of these is a large–arbor, large–soma, α–like cell. The number of other subtypes we have stained, and their morphological details, remain to be determined.
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