Fig. 4.

Type 1 neurons are transiently inhibited during phasic inflation but show no change in preinspiratory activity.A, Raw traces of type 1 neuron membrane potential with and without phasic inflation are displayed as in Figure 3. In control cycles, type 1 neurons have a ramp-like depolarization during expiration and can begin to spike before ventral root inspiratory onset. Although preinspiratory trajectories with and without inflation coincide closely, in the presence of phasic inflation there is pronounced postinspiratory hyperpolarization coinciding with inflation (arrows). B, Burst-triggered average of seven cycles from one type 1 neuron, displayed as in Figure 3.Bar and column graphs show mean values for all eight type 1 neurons and are scaled to the axes of the averaged traces. Phasic inflation causes postinspiratory inhibition; theblack column to the right shows average postinspiratory inhibition in type 1 neurons (−5.8 ± 0.7 mV), which lasted 710 ± 100 msec (bottom, black bar). Phasic inflation significantly shortens (p < 0.01) type 1 inspiratory firing duration, from 1000 ± 120 msec (top, white bar) to 460 ± 60 msec (top, black bar).