54
HCN Isoform ½∕2±std (mV) τ±std @ -94 mV (ms)
Rod∕⅛ |
-77 ± .78 (n=10) |
52.3 ± 9.5 (n=4) |
Cone Ih |
-74 ± 1.1 (n=10) |
50.7 ± 8.0 (n=8) |
HCNl |
-69 |
84 |
HCN2 |
-95 |
557 |
HCN3 |
. -77 |
1408 |
HCN4 |
-81 |
3586 |
Table 3.1 : Kinetic parameters for ∕⅛ and HCN isoforms. Kinetic data for both rods and
cones are similar, and comparable to parameters from the HCNl isoform. Data for HCN 1-
4 come from measurements from homogeneous expression systems (Altomare et al., 2001,
Stieber et al., 2005). The half activation voltage for HCNl is known to be ~5 mV more
hyperpolarized in in-vivo systems than in the expression system (Altomare et al., 2001),
putting it on par with measured salamander Ih.