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Figure 7 | Neural Development

Figure 7

From: Distinct perinatal features of the hyperpolarization-activated non-selective cation current Ih in the rat cortical plate

Figure 7

Functional implications and resonance behavior of layer V neocortical neurons at P0 and P30. (A) Varying the interpulse interval in the current-clamp between ‘infinite’ (initial), 2 seconds or 5 seconds reduced the sag amplitude as a result of the slowed deactivation. Depicted traces were recorded after injection of −50 pA. (B) Dependence of Ih activation and an instantaneous component on the interval of consecutive voltage steps to −130 mV of an ‘infinite’ (initial), 3-second or 5-second interval. (C/F) Examples of the membrane voltage of a neuron at P0 (C, top) and at P30 (F, top) as a response to ZAP current injection (bottom). Note the lack of a distinguishable peak despite the frequency increase to 20 Hz in P0 neurons. (D/G) Calculated impedance in relation to the frequency for the cells depicted in (C) and (F). Note the absence of a distinct membrane resonance peak and the relatively high impedance values at P0 (D) as compared to the distinct peak at approximately 3 Hz and lower impedance at P30 (G). At both age groups data points were averaged from three consecutive ZAP recordings. Insets: Impedance phase shifts in relation to the frequency. (E/H) Modeling (membrane voltage of −70 mV) using the entire parameter set for either a P0 or P30 neuron (black lines) mimicked the results of the ZAP recordings of rat neocortical neurons in brain slices. (E) Changing the kinetics to values of a P30 neuron (red line) or adjusting the conductance to a P30 neuron (yellow line) resulted in distinct resonance peaks, whereas replacement of the half-maximal activation by P30 values (grey line) or substituting the passive properties to values at P30 (blue line) led to massive impedance changes. (H) In contrast, replacing the simulation values at P30 by only the kinetic properties of a P0 neuron still resulted in a resonance peak, though less distinct (red line). Insets: Impedance phase shifts in relation to the frequency calculated from the simulated data. Only neurons at P30 showed a peak positive phase value and therewith a crossover from positive to negative phase in the impedance phase profiles.

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