Ventilatory response of the cat to hypoxia in sleep and wakefulness

Abstract

This study characterized ventilation, the airflow waveform, and diaphragmatic activity in response to hypoxia in the intact adult cat during sleep and wakefulness. Exposure to hypoxia for up to 3 h caused sustained hyperventilation during both wakefulness and sleep. Hyperventilation resulted from significant increases in minute ventilation due to increases in both tidal volume and frequency. Diaphragmatic activity changed significantly from augmenting activity with little postinspiratory-inspiratory activity (PIIA) in normoxia to augmenting activity with increased PIIA in hypoxia. The increase in PIIA was least in rapid eye movement sleep. These changes in diaphragmatic activity were associated with changes in airflow waveforms in inspiration and expiration. We conclude that the ventilatory response to hypoxia involves a change in the output of the central pattern generator and that the change is dependent in part on the state of consciousness.

MK-801 alters diaphragmatic activities in unanesthetized rats differently between normoxia and hypoxia

“…We observed abnormal behavior (e.g., head nodding and waving, and salivation) after MK-801 administration, as has been reported in previous studies (Lewis et al, 1989;Löscher et al, 1991;Löscher and Hönack, 1992), suggesting that these characteristic behavioral changes could increase metabolic demand (Roussel et al, 1992) and slightly decrease blood pH. Although MK-801 is known as a potent NMDA antagonist (Wong et al, 1986), occurrence of such characteristic behavioral syndrome in unanesthetized rats suggests that MK-801 induces some changes in catecholaminergic systems and serotonergic neurontansmission (Löscher and Hönack, 1992), and in the state of consciousness, which may influence breathing pattern in unanesthetized animals (Campbell and Feinberg, 1999;Lovering et al, 2003).…”

“…EMGdia in this study, may be more reliable than indirect measurement of ventilation using whole-body plethysmography to detect alterations in respiratory timing. Although augmented postinspiratory inspiratory activity (PIIA) may be detected in hypoxia (Sherrey et al, 1988;Lovering et al, 2003) and may complicate analysis of respiratory timing in EMGdia recording, we did not obtain consistently increasing PIIA during EMGdia measurement. In contrast, the measurements using whole-body plethysmography in earlier studies (Ohtake et al, 1998;Reid and Powell, 2005) may have detected the movement of other respiratory muscles, which were not detected by EMGdia in this study.…”

“…To eliminate the potential influence of SABs on the breathing pattern (Reynolds and Hilgeson, 1965; Orem and Trotter, 1993; Lovering et al, 2003) and circulation (Marshall and Metcalfe, 1988), we excluded five breaths before and after each occurrence of SAB in the analysis of TI, TE, and TTOT.…”

Neural Control of Breathing and CO2 Homeostasis

“…However, as recently achieved for RTN, a critical test of this hypothesis will require identification of the molecular bases for their pH sensitivity, and demonstration that selective elimination of that sensing mechanism (rather than wholesale inhibition or destruction of the neurons) attenuates the respiratory chemoreflex. The most obvious changes in the activity of serotonergic neurons in vivo are state-related (Jacobs and Azmitia, 1992) and serotonin loss-of-function experiments may partially reproduce the generally depressant effects of REM sleep on muscle tone, breathing, autonomic functions and thermogenesis (Berthon-Jones and Sullivan, 1984; Horner et al, 2002; Lovering et al, 2003; Teran et al, 2014). Thus, lower brainstem serotonergic neurons likely contribute to arousal state-dependent modulation of multiple systems, including breathing.…”

Neural Control of Respiration by the Retrotrapezoid Nucleus.

“…For example, although the respiratory chemoreflexes still operate during REM sleep, the breathing frequency (f R ) is typically unaffected by hypoxia or hypercapnia (Coote, 1982;Berthon-Jones & Sullivan, 1984;Horner et al, 2002;Lovering et al, 2003;Nakamura et al, 2007). Also, in conscious cats ventilated to apnea during non-REM sleep, diaphragmatic EMG reemerges during REM sleep (Orem et al, 2005).…”