Cholinergic and dopaminergic amacrine cells differentially express calcium channel subunits in the rat retina.

Immunofluorescence labeling was performed to study the expression of high voltage-activated Ca(2+) channel subunits on rat retinal cholinergic and dopaminergic amacrine cells, which were double labeled with antibodies against choline acetyltransferase and tyrosine hydroxylase, respectively. The alpha(1A) subunit was predominantly expressed on the processes but not on the somata of cholinergic amacrine cells, whereas staining for alpha(1B) and alpha(1E) was observed in both structures of the cells. Immunoreactivity of alpha(1C) and alpha(1D) was not found in the cholinergic amacrine cells. Dopaminergic amacrine cells, on the other hand, exhibited a differential expression pattern of the Ca(2+) channel subunits, with alpha(1A), alpha(1C) and alpha(1E) being expressed on both somata and processes and alpha(1B) predominantly on the processes of the cells. No alpha(1D) labeling was seen. These results suggest that Ca(2+) channel subunits differentially expressed on the cholinergic and dopaminergic amacrine cells may endow these two cell types with different physiological properties.