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. 2007 Nov 14;27(46):12440–12451. doi: 10.1523/JNEUROSCI.2358-07.2007

Figure 4.

Figure 4.

HCN1 channels suppress low-frequency subthreshold membrane potential fluctuations but are not required for perithreshold theta frequency fluctuations. A, B, Example of membrane potential responses of stellate cells from HCN1+/+ (A) and HCN1−/− (B) mice to series of positive current steps. Responses that contain spikes are in gray. For clarity, only a subset of the responses are shown. Traces on the right show a section of the same data on an expanded time base. C, D, Spectrograms (left) of membrane potential activity from depolarized (top left) and relatively hyperpolarized (bottom left) traces and corresponding power spectra (right) for the data in A and B. The zero time point in each spectrogram corresponds to the onset of the positive current step. The power spectra are for the membrane potential fluctuations from 4 to 20 s after the onset of the current step. In each spectrogram, the relative power is plotted as a function of time (abscissa) and frequency (ordinate). E, SD of the membrane potential plotted as a function of mean membrane potential. ANOVA revealed a significant effect of genotype (p = 5.8 e-13), membrane potential (p = 2.2 e-16), and interaction between genotype and membrane potential (p = 0.028). Subsequent t tests indicated significant (p < 0.05) differences between HCN1+/+ and HCN1−/− mice at potentials negative to −56 mV. F–H, Mean power in the range of 1–4 Hz (F), 4–8 Hz (G), and 8–12 Hz (H) plotted as a function of membrane potential. ANOVA revealed a significant effect of genotype and membrane potential in the 1–4 Hz band (genotype, p = 1.8 e-05; membrane potential, p = 3.6 e-16; interaction, 0.96) but only of membrane potential in the 4–8 Hz band (genotype, p = 0.92; membrane potential, p = 2.2 e-16) and 8–12 Hz band (genotype, p = 0.0765; membrane potential, p = 2.2 e-16). Subsequent t tests revealed a significant difference (p < 0.05) in the SD of the membrane potential between HCN1+/+and HCN1−/− mice in the 1–4 Hz band at potentials negative to −54 mV but no difference at any potential in the 4–8 or 8–12 Hz bands.