How does HCN isoform expression during development govern Ih properties?
To correlate HCN expression levels and membrane current for matching postnatal ages, Ih current density (extrapolated from the fit in Fig. 1B) was plotted against the sum of the detected radioactivity (determined by ISH for P2, P11, and P60) (Fig. 3A) and the HCN/β-actin ratio (determined by Western blotting for P7, P30, and P90) (Fig. 3B) of all three isoforms. This yielded a linear relationship for both current density and summed mRNA levels (r2 = 0.999) (Fig. 3C) as well as for current density and summed protein levels (r2 = 0.994) (Fig. 3D). Functional consequences of increased HCN isoform expression One hallmark of Ih current activation during current-clamp recordings is the depolarizing voltage sag generated during the course of hyperpolarizing current steps (Pape, 1996). Furthermore, TC neurons can act as intrinsic oscillators in the delta frequency range (0.5–4 Hz) during slow-wave sleep (when oscillations are in the same delta frequency) based on the cyclic interaction between
