Abstract
Abstract: :
Purpose: DARPP-32, a dopamine- and cyclic AMP-regulated phosphoprotein with an apparent molecular weight of 32,000, is part of the D1 dopamine receptor signal transduction. This study was conducted in order to identify the distribution of D1 dopamine receptor and DARPP-32 in monkey retina. Methods: Eyes were removed from anesthetized monkeys (Macaca fascicularis). Retina was immediately embedded in OCT compound and snap-frozen. Frozen sections 8 µm in thickness were cut using a cryostat microtome, fixed with 4% paraformaldehyde, and processed for double labelling immunohistochemistry. Anti-DARPP-32 antibody (Ab), anti-D1 dopamine receptor Ab and anti-glial fibrillary acidic protein(GFAP) Ab, which is a marker for Muller cells, were used. Results: The staining of DARPP-32 was observed in the inner nuclear layer and outer nuclear layer. The D1 dopamine receptor colocalized with DARPP-32, but not all D1 dopamine positive cells expressed DARPP-32 in the inner nuclear layer. In the outer nuclear layer, the staining of D1 dopamine receptor was barely detectable, while that of DARPP-32 was intense. Double labeling using anti-GFAP Ab and anti-DARPP-32 Ab revealed that a few DARPP-32 positive cells showed the staining of anti-GFAP Ab. Conclusion: These results demonstrated the regulation of DARPP-32 by D1 dopamine activation in the monkey retina. The demonstration of a large population of retinal neuron that contain DARPP-32 but apparently do not contain D1 dopamine receptor substantiated the premise that these cells have an alternative pathway.
Keywords: 389 dopamine • 554 retina • 474 microscopy: light/fluorescence/immunohistochemistry