Sleep-related apneic and apneustic breathing following pneumotaxic lesion and vagotomy

Sleep-wakefulness state was found to be a crucial determinant of respiratory pattern in chronic cats with bilateral lesions of the rostral pontine pneumotaxic complex (PC). Lesions resulted in increased TE, TI, and VT in all sleep and waking states. Several state-specific respiratory effects were also observed: (1) comparatively eupneic breathing during alert wakefulness (WI); (2) greatly increased TE in slow wave sleep (SWS); (3) decreased TE during rapid eye movement sleep (REM), relative to SWS; (4) increased tendency for prolonged TI (brief apneusis) during REM. Bilateral vagotomy at 2-5 weeks after PC lesion exaggerated these effects and caused distinct apneusis during REM. The results confirm that the PC is not essential for the occurrence of either rhythmic breathing or for expression of state changes in respiration, although the effects of the PC on breathing in the intact cat may vary as a function of sleep-wakefulness state. It is suggested that other regulatory systems that influence the central respiratory rhythm generator (RRG) are similarly modulated by state, and that variations in respiratory pattern observed following PC lesion and vagotomy are the result of state-dependent changes in the balance between multiple inputs to the RRG.