The name is absent

49

vation curve and time course, and that these values are characteristic of the HCNl isoform
(figure 3.1 Al-4, Bl-4). Our whole-cell data from salamander rods is similar to reports from
other researchers [1, 75, 78, 54], however, we use the intact retina to avoid the drawbacks of
dissociated cells and standardize recording conditions for rods and cones. With whole-cell
voltage clamp, we demonstrate that the activation time course of rod and cone 7⅛ is similar to
homogeneously expressed HCNl channels (figure 3.1 A3, B3, table 3.1). Although the rod
and cone half activation potentials are more hyperpolarized than the expressed HCN1 chan-
nels, this is a known difference between in vivo vs. expressed HCNl channels [3]. While
other researchers have shown that the HCNl isoform is responsible for Ih in rabbit rods
[31], we demonstrate that this is true not only for salamander rods, but also for cones. Our
immunohistochemical and western blot experiments support our finding that HCN1 chan-
nels are responsible for the 1⅛ current in rods and cones (figure 3.2). These results, which
agree with experiments on the rat retina [83], show anti-HCNl antibodies strongly labeling
rods and cones. Our western blot experiments show the HCNl antibody binds to a 60 kDa
protein, which was also noted by Müller et al in the rat retina [83]. Given the specificity
predicted by a BLASTp search (see Results and Mehtods) and demonstrated in the blot itself
(figure 3.2 Al), we believe the 60 kDa protein represents a truncated form of HCNl in the
retina. Whether this product is active or not warrants further investigation.

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