Figure 11.

Hyperpolarization-activated inward currents (I_h) in the post-inspiratory laryngeal motoneurones

Aa, voltage clamp recording of one representative post-inspiratory laryngeal motoneurone from control rats showing that hyperpolarizing voltage steps (−10 mV increments), from a holding potential of −70 mV, evoked a time-dependent inward current. Ab, inward current is reduced by addition of ZD7288 (40 μm), a selective blocker of the I_h, to the perfusion solution. Ac, off-line subtraction of the traces presented in (Aa) and (Ab) is showing the ZD7288-sensitive I_h. B, current–voltage relationship of the steady-state portion of the averaged I_h in the post-inspiratory laryngeal motoneurones from control and CIH rats. C, I_h activation curve (Boltzman fitted; see Methods) showing its voltage dependence. D, voltage transients of one post-inspiratory laryngeal motoneurone representative of control rats in response to hyperpolarizing current injections. Upon larger hyperpolarizing pulses, the membrane potential relaxed towards more positive values as a time-dependent conductance slowly turned on (*sag; left panel). Addition of ZD7288 to the perfusion blocked the hyperpolarization-activated conductance and eliminated the sag (right panel). CIH, chronic intermittent hypoxia.