Molecular identification of sodium channels in goldfish retina and in bipolar neurons. A, Predicted amino acid sequences for sodium channel α subunits identified by RT-PCR from mRNA extracted from goldfish retina. Thedots indicate residues at which all three α subunits are identical. Regions in which two or more residues are identical are shaded gray. Gaps are indicated bydashes. The asterisk indicates the location of an insertion representing a putative splice variant of gfNa_v1.2. The predicted amino acid sequence of the insertion is shown below. B, Agarose gel electrophoresis of sodium channel cDNAs obtained by RT-PCR from single bipolar neurons. Each numbered lane shows the result from a single cell. The molecular weight markers correspond to 300, 400, 500, 650, 850, and 1000 bp. The predicted size of the amplified cDNA for sodium channels is 530–550 bp. Lanes 3 and 11 show control cells in which the reverse transcriptase enzyme was omitted. In the remaining lanes, cDNA of the predicted size was detected in 5 of 10 bipolar cells.