Fig. 1.

Sample recordings showing airflow rate (top traces in each panel; inspiration represented by downward deflections) and inspired tidal volume (Vt; bottom trace in each panel) from representative neonatal rat pups studied on postnatal day 1 (P1), P3, and P12. All recordings were taken while the animal was breathing compressed, humidified air. Recordings for both prenatal saline-exposed (left) and prenatal nicotine-exposed (PNE; right) pups are shown for comparison. Horizontal lines through the flow recordings represent zero flow. The plethysmographs were calibrated by injecting known volumes of gas and digitally integrating the inspiratory flow (V̇i) signal with respect to time, yielding inspired Vt (described in detail in methods); thus the flow trace is uncalibrated. Small differences in frequency and volume between saline-exposed and nicotine-exposed pups under these conditions were not a consistent finding, as the average data demonstrate (Fig. 2).