Fig. 6.

Tg8 mice are less sensitive to lung inflation than C3H mice. A, Recordings from the Dia global EMGs in a C3H mouse (left panel) and a Tg8 mouse (right panel) during 1 sec tracheal occlusions (occl.) performed at the very end of the inspiration. The first gray bar indicates the duration of the expiration preceding the tracheal occlusion and is displayed with the next expiration to indicate the delay of the inspiratory on-switch produced by the tracheal occlusion. B, During expiration, the lungs are overinflated by injecting a known volume of air (in microliters) that is increased until the inspiratory on-switch is delayed up to the end of the 2 sec occlusion. Recordings from the Dia global EMGs in a C3H mouse (left panel) and a Tg8 mouse (right panel) during these 2 sec occlusions show that the volume-thresholds to delay the inspiratory on-switches are higher in Tg8 than in C3H mice. C, Electrical stimulation of the pulmonary vagal afferents at the central end of the severed vagus nerve for 2 sec (stim., 100 Hz) elicits a similar inhibition of the Dia global EMGs in a C3H mouse and a Tg8 mouse.