25
mV
Figure 3.1 : Whole cell currents from voltage-clamp recordings from rod (A) and cone (B).
(Al) and (Bl) show example current traces. (A2) and (B2) showthe median IV curve values
with vertical bars representing the minimum and maximum range for 10 cells. (A3) and
(B3) show the respective activation curves computed from the normalized and averaged
tail currents of 10 cells. Data is fit with a sigmoidal exponential function of the form: g =
b + gmaχ∕(y + e^v~vhal^∣slσpe}. (A4) and (B4) show the activation time constants fit with a
single exponential for rod (A4) and cone (B4) data (black dots), with the color lines showing
values for HCNl,2,3, and 4. In (A3,4) and (B3,4), data for HCN 1, 2, and 4 come from
homogeneously expressed HCN channels (Altomare et al., 2001) plus estimated values for
expressed HCN3 (Stieber et al., 2005)