Localization of Rod Bipolar Cells in the Mammalian Retina Using an Antibody Against the α(1)c L-type Ca(2+) Channel

Bipolar cells transmit stimuli via graded changes in membrane potential and neurotransmitter release is modulated by Ca(2+) influx through L-type Ca(2+) channels. The purpose of this study was to determine whether the α(1)c subunit of L-type voltage-gated Ca(2+) channel (α(1)c L-type Ca(2+) channel) colocalizes with protein kinase C alpha (PKC-α), which labels rod bipolar cells. Retinal whole mounts and vertical sections from mouse, hamster, rabbit, and dog were immunolabeled with antibodies against PKC-α and α(1)c L-type Ca(2+) channel, using fluorescein isothiocyanate (FITC) and Cy5 as visualizing agents. PKC-α-immunoreactive cells were morphologically identical to rod bipolar cells as previously reported. Their cell bodies were located within the inner nuclear layer, dendritic processes branched into the outer plexiform layer, and axons extended into the inner plexiform layer. Immunostaining showed that α(1)c L-type Ca(2+) channel colocalized with PKC-α in rod bipolar cells. The identical expression of PKC-α and α(1)c L-type Ca(2+) channel indicates that the α(1)c L-type Ca(2+) channel has a specific role in rod bipolar cells, and the antibody against the α(1)c L-type Ca(2+) channel may be a useful marker for studying the distribution of rod bipolar cells in mouse, hamster, rabbit, and dog retinas.