Fig. 1

A–D Respiratory activity in a vagotomized neonatal rat. Electromyograms were obtained from the diaphragm (Dia) and abdominal muscles (Abd). The integrated electromyogram of Abd (∫Abd, time constant 0.1 s) is also shown as the third trace in panel D. The concentration of isoflurane was decreased from 2 to 0% at the time indicated in panel A. B–D Portions of recording A above the horizontal bars marked B–D are shown on an expanded time scale. The vertical gain in Abd in B is higher by a factor of four compared with other records. As indicated by the black circle in B, the inspiratory burst was absent in some respiratory cycles under 2% isoflurane. The arrows indicate E1 and E2 activities. The amplitudes of E2 and E1 activities (E2 amp, E1 amp) were measured from the baseline or trough to the peak